feat(lanes,ui): per-lane git surface — Changes panel, VS Code-style diff, branch-aware Add lane, redesigned tooltips (#34, #35)

- Changes card beside lane detail with five modes: Files tree, overview,
  Review (whole diff, per-file collapse), single file, commit history.
- LaneDiffView: unified / side-by-side with independent scroll on both axes
  and mirrored scrollLeft, expand/collapse context, intra-line emphasis.
- Staged-only commit box; git actions (fetch/pull/push/stage/unstage/
  discard/commit/switch/branch-create/branch-delete) guarded in git-ops.js.
- Server: git-diff.js + git-ops.js behind GET /api/lanes/:id/git/* and
  POST /api/lanes/:id/git/:action; gitFacts gains upstream/ahead/behind.
- Add lane: new/existing branch, current branch, worktree list, prefill
  from the git bar's "New lane here"; /api/run/cwds gains a repo kind.
- GlobalTooltip upgrades every native title into a themed anchored bubble;
  chart/info popovers use theme tokens.

openapi.yaml

@@ -3,7 +3,7 @@
 openapi: 3.0.3
 info:
   title: Agent Dashboard for Claude Code API
-  version: 1.7.0
+  version: 1.8.1
   description: HTTP API for real-time Claude Code session monitoring, agent lifecycle tracking, analytics, pricing, hooks ingestion, and workflow intelligence.
   contact:
     name: Nguyễn Ngọc Trí Vĩ
@@ -10977,9 +10977,256 @@ paths:
           description: Absolute path to an existing git repository.
       responses:
         '200':
-          description: '{branches: string[], current: string | null}.'
+          description: '{branches: string[], current: string | null, worktrees: {path, branch?, locked?}[]}. The worktrees ride along so the picker can grey out branches git would refuse to check out twice.'
         '400':
           description: repo is missing, relative, does not exist, or is not a git repo.
+  /api/lanes/{id}/git/changes:
+    get:
+      tags:
+        - Lanes
+      summary: A lane's code changes, at one of three depths
+      description: Backs the Workspace Changes panel. No extra params = a summary of every changed file; full=1 adds every file's hunks (review mode); path=<file> returns that one file's hunks. range=work (default) is HEAD vs the working tree with untracked files included; range=branch is <base_branch>...HEAD; range=commit needs sha= and shows that one commit. context= widens each hunk (default 3, clamped to 5000) — the viewer's expand button. Lines arrive with both gutters resolved. Capped at 300 files, 200 KB of patch per file and 1 MB per full read; a cap that bit sets `truncated`. Read-only, no same-origin guard.
+      operationId: getLaneChanges
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+        - name: range
+          in: query
+          schema:
+            type: string
+            enum:
+              - work
+              - branch
+              - commit
+            default: work
+        - name: sha
+          in: query
+          schema:
+            type: string
+          description: 'range=commit only: the commit to show.'
+        - name: context
+          in: query
+          schema:
+            type: integer
+            default: 3
+            maximum: 5000
+          description: Unchanged lines around each hunk.
+        - name: path
+          in: query
+          schema:
+            type: string
+          description: Return only this file, with its hunks.
+        - name: full
+          in: query
+          schema:
+            type: string
+            enum:
+              - '1'
+              - 'true'
+          description: Include every file's hunks (review mode).
+      responses:
+        '200':
+          description: '{available, range, base, baseRef, sha, context, files, truncated}, or {available:false} for a cwd git cannot read.'
+        '400':
+          description: ENOBASE (range=branch on a lane with no base branch), ENOFILECHANGE (path has no changes in this range), EBADRANGE or EBADREV.
+        '404':
+          description: Lane not found.
+  /api/lanes/{id}/git/log:
+    get:
+      tags:
+        - Lanes
+      summary: The lane's recent commits
+      description: Newest first, up to limit (default 30, max 200). file= narrows it to the commits touching one path. Reading a commit's diff is GET /api/lanes/{id}/git/changes?range=commit&sha=. Read-only, no same-origin guard.
+      operationId: listLaneCommits
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+        - name: limit
+          in: query
+          schema:
+            type: integer
+            default: 30
+            maximum: 200
+        - name: file
+          in: query
+          schema:
+            type: string
+      responses:
+        '200':
+          description: '{available, commits:[{sha, short, subject, author, date, refs}]}.'
+        '404':
+          description: Lane not found.
+  /api/lanes/{id}/git/file:
+    get:
+      tags:
+        - Lanes
+      summary: One file's whole content at a revision
+      description: rev=work (the file on disk, untracked included), HEAD, or a commit-ish. The `work` revision is the only one that reads the filesystem and it is realpath-confined to the lane directory. Binary content is reported, never returned. Capped at 1 MB. Read-only, no same-origin guard.
+      operationId: readLaneFile
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+        - name: path
+          in: query
+          required: true
+          schema:
+            type: string
+        - name: rev
+          in: query
+          schema:
+            type: string
+            default: work
+      responses:
+        '200':
+          description: '{available, path, rev, binary, truncated, lines}.'
+        '400':
+          description: EBADPATH, EBADREV or ENOFILE.
+        '404':
+          description: Lane not found.
+  /api/lanes/{id}/git/ls:
+    get:
+      tags:
+        - Lanes
+      summary: Tracked paths matching a substring (quick-open)
+      description: Reads `git ls-files`, so ignored files never appear and no skip-list is maintained. Basename hits rank first. Capped at 500 paths. Read-only, no same-origin guard.
+      operationId: listLanePaths
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+        - name: q
+          in: query
+          schema:
+            type: string
+      responses:
+        '200':
+          description: '{available, paths, truncated, total}.'
+        '404':
+          description: Lane not found.
+  /api/lanes/{id}/git/tree:
+    get:
+      tags:
+        - Lanes
+      summary: One directory level of tracked files
+      description: 'The file explorer''s expand-a-folder read: tracked entries under path=, folded into directories at that level. Read-only, no same-origin guard.'
+      operationId: listLaneTree
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+        - name: path
+          in: query
+          schema:
+            type: string
+            default: ''
+      responses:
+        '200':
+          description: '{available, path, entries:[{name, path, dir}], truncated}.'
+        '400':
+          description: EBADPATH (the path escapes the lane).
+        '404':
+          description: Lane not found.
+  /api/lanes/{id}/git/branches:
+    get:
+      tags:
+        - Lanes
+      summary: The lane repo's own local branches
+      description: Feeds the lane's branch switcher. The repository comes from the lane row, never from the query — that is what GET /api/lanes/branches is for. Read-only, no same-origin guard.
+      operationId: listLaneOwnBranches
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+      responses:
+        '200':
+          description: '{available, branches, current, worktrees}.'
+        '404':
+          description: Lane not found.
+  /api/lanes/{id}/git/{action}:
+    post:
+      tags:
+        - Lanes
+      summary: One git write on the lane's working copy
+      description: 'fetch (--all --prune), pull (ALWAYS --ff-only — a diverged branch is reported, never merged), push (-u origin HEAD, so only the branch the lane is on), stage/unstage (per file), discard (per file; irreversible, so it REQUIRES confirm:true), commit (git add -A then commit -m <message>, or only:"staged" to take the index as it stands), switch (git switch, -c to create; refuses a dirty tree so an agent''s half-finished work is never carried onto another branch), and branch-create / branch-delete (create never switches; delete is `git branch -d`, refuses main/master/development/develop, the current branch and one held by another worktree). A path in the body must be one `git status` is reporting as changed, so no path outside the lane is reachable. Guarded and serialized per lane under the lane lock. Deliberately no merge, rebase, reset or stash: reset stays behind the destroy guard on POST /api/lanes/{id}/reset. Network actions are killed after 60s.'
+      operationId: runLaneGitAction
+      parameters:
+        - name: id
+          in: path
+          required: true
+          schema:
+            type: integer
+        - name: action
+          in: path
+          required: true
+          schema:
+            type: string
+            enum:
+              - fetch
+              - pull
+              - push
+              - stage
+              - unstage
+              - discard
+              - commit
+              - switch
+              - branch-create
+              - branch-delete
+      requestBody:
+        required: false
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                message:
+                  type: string
+                  description: commit only; required, max 4000 chars.
+                only:
+                  type: string
+                  enum:
+                    - staged
+                  description: commit only; commit the index as it stands, with no add -A.
+                branch:
+                  type: string
+                  description: switch, branch-create and branch-delete.
+                base:
+                  type: string
+                  description: branch-create only; defaults to HEAD.
+                create:
+                  type: boolean
+                  description: switch only; create the branch.
+                paths:
+                  type: array
+                  items:
+                    type: string
+                  description: stage, unstage, discard; each must be a path git reports changed.
+                confirm:
+                  type: boolean
+                  description: discard only; the call is refused without it.
+      responses:
+        '200':
+          description: '{action, ok:true, output} — git''s own stdout+stderr.'
+        '400':
+          description: EBADACTION, EBADMESSAGE, EBADBRANCH, EBADPATH, ECONFIRM, EPROTECTED, ENOBRANCH, EBRANCHEXISTS, EBRANCHBUSY, EDIRTY or ENOCHANGES.
+        '404':
+          description: Lane not found.
+        '500':
+          description: git failed; its stderr is appended to error.message.
   /api/lanes/{id}/{action}:
     post:
       tags: