feat(workspace): a session in its own worktree, Claude's way

Desktop-parity phase 6, following Claude Desktop:
- the workspace home's Worktree checkbox starts the pane with
  `claude --worktree=<name>`, so Claude Code makes, populates
  (.worktreeinclude, WorktreeCreate hook) and cleans up
  <repo>/.claude/worktrees/<name>; AgentHub only excludes
  /.claude/worktrees/ at the repo root (Claude does not)
- server/lib/session-worktree.js resolves a session's worktree from the
  session row only (owned by the workspace, registered by git worktree
  list); every lane git route takes ?session= and answers ENOWORKTREE
  instead of falling back to the main folder
- the session view's Changes panel works in the opened run's worktree
  (dashboard_runs.worktree, GitTarget in the client api)
- Resume/Fork start in the session's worktree; a gone one is ENOWORKTREE
- Archive of a worktree session removes the worktree after asking:
  git worktree remove without --force, git branch -d (unmerged work keeps
  its branch), a lock held by a live pid refused, a stale one cleared
- listWorktrees reads `locked <reason>` locks
- tests scrub GIT_* env so the pre-commit suite cannot act on this repo

client/src/components/lanes/LaneChangesPanel.tsx

@@ -59,7 +59,7 @@ import {
   Trash2,
   UnfoldVertical,
 } from "lucide-react";
-import { api } from "../../lib/api";
+import { api, gitTarget } from "../../lib/api";
 import { pasteToLane } from "../../lib/panePaste";
 import { LaneDiffView, LaneFileView, type DiffLayout, type LaneDiffChange } from "./LaneDiffView";
 import { LaneConflictView } from "./LaneConflictView";
@@ -422,11 +422,16 @@ function ChangeRow({
 
 export function LaneChangesPanel({
   laneId,
+  session,
   onNewLane,
   full = false,
   tab = "changes",
 }: {
   laneId: number;
+  /** Show and act on that session's own worktree (`claude --worktree`)
+   *  instead of the workspace's folder. The Workspace keys the panel on it,
+   *  so a different session is a fresh panel. */
+  session?: string;
   /** The Workspace right panel's activity-bar tab: `files` is the browse mode
    *  on its own (no git header, no mode switcher), `changes` the other four.
    *  At full width both show the explorer sidebar beside the changes. */
@@ -440,7 +445,9 @@ export function LaneChangesPanel({
   const { t } = useTranslation(["lanes"]);
   // One read of the working copy, shared by the header and every write below:
   // a stage, a discard or a commit changes the counts the header shows.
-  const [git, refreshGit] = useLaneGitFacts(laneId);
+  const [git, refreshGit] = useLaneGitFacts(laneId, session);
+  // Every git read and write below goes to the same tree as those facts.
+  const target = gitTarget(laneId, session);
   // A diff line's comment goes into this workspace's pane, as a paste.
   const comment = useCallback((text: string) => pasteToLane(laneId, text), [laneId]);
   // Bumped by Refresh and by a git bar action: a pull or a switch moves
@@ -544,7 +551,7 @@ export function LaneChangesPanel({
     const seq = ++loadSeq.current;
     setLoading(true);
     try {
-      const result = await api.lanes.changes(laneId, {
+      const result = await api.lanes.changes(target, {
         range,
         ...(range === "commit" && sha ? { sha } : {}),
         ...(mode === "file" && openFile ? { path: openFile, context } : {}),
@@ -591,7 +598,7 @@ export function LaneChangesPanel({
   useEffect(() => {
     if (mode !== "history") return;
     void api.lanes
-      .gitLog(laneId, { limit: 50 })
+      .gitLog(target, { limit: 50 })
       .then(forLane(laneId, (r) => setCommits(r.commits)))
       .catch((err) => setError(err instanceof Error ? err.message : String(err)));
   }, [mode, laneId, reread]);
@@ -603,7 +610,7 @@ export function LaneChangesPanel({
     const wanted = full || (mode === "browse" && !query.trim());
     if (!wanted || treeRootLoaded) return;
     void api.lanes
-      .gitTree(laneId, "")
+      .gitTree(target, "")
       .then(forLane(laneId, (r) => setTreeChildren((prev) => ({ ...prev, "": r.entries }))))
       .catch((err) => setError(err instanceof Error ? err.message : String(err)));
     // `treeChildren` itself is the cache this fills — a dep on it would loop.
@@ -619,7 +626,7 @@ export function LaneChangesPanel({
     });
     if (path in treeChildren) return;
     void api.lanes
-      .gitTree(laneId, path)
+      .gitTree(target, path)
       .then(forLane(laneId, (r) => setTreeChildren((prev) => ({ ...prev, [path]: r.entries }))))
       .catch((err) => setError(err instanceof Error ? err.message : String(err)));
   };
@@ -632,7 +639,7 @@ export function LaneChangesPanel({
     const lane = laneId;
     setTreeBusy(true);
     try {
-      const { levels } = await api.lanes.gitTreeAll(lane);
+      const { levels } = await api.lanes.gitTreeAll(target);
       // A lane switch mid-read must not land lane A's tree in lane B.
       if (laneNow.current !== lane) return;
       setTreeChildren(levels);
@@ -655,7 +662,7 @@ export function LaneChangesPanel({
     let live = true;
     const timer = window.setTimeout(() => {
       void api.lanes
-        .gitLs(laneId, q)
+        .gitLs(target, q)
         .then((r) => live && setHits(r.paths))
         .catch(() => live && setHits([]));
     }, 150);
@@ -670,7 +677,7 @@ export function LaneChangesPanel({
   useEffect(() => {
     if (mode !== "file" || !whole || !openFile) return;
     void api.lanes
-      .gitFile(laneId, openFile, range === "commit" && sha ? sha : "work")
+      .gitFile(target, openFile, range === "commit" && sha ? sha : "work")
       .then(
         forLane(laneId, (r) =>
           setText(
@@ -775,7 +782,7 @@ export function LaneChangesPanel({
     setBusy(true);
     setError(null);
     try {
-      const r = await api.lanes.gitSaveFile(lane, text.path, draft, text.sha);
+      const r = await api.lanes.gitSaveFile(target, text.path, draft, text.sha);
       if (laneNow.current !== lane) return;
       if (r.available) {
         setText({ path: r.path, lines: r.lines, truncated: r.truncated, sha: r.sha });
@@ -803,7 +810,7 @@ export function LaneChangesPanel({
     setError(null);
     try {
       const paths = Array.isArray(path) ? path : [path];
-      await api.lanes.gitAction(lane, action, { paths, ...(confirm ? { confirm } : {}) });
+      await api.lanes.gitAction(target, action, { paths, ...(confirm ? { confirm } : {}) });
       if (laneNow.current !== lane) return;
       setConfirmDiscard(null);
       refreshGit();
@@ -824,7 +831,7 @@ export function LaneChangesPanel({
     setBusy(true);
     setError(null);
     try {
-      await api.lanes.gitAction(lane, action, body);
+      await api.lanes.gitAction(target, action, body);
       if (laneNow.current !== lane) return;
       setArmedAbort(false);
       refreshGit();
@@ -849,7 +856,7 @@ export function LaneChangesPanel({
     setBusy(true);
     setError(null);
     try {
-      await api.lanes.gitAction(lane, action, {
+      await api.lanes.gitAction(target, action, {
         path,
         hunk: change.hunk.header,
         block: change.block,
@@ -916,7 +923,7 @@ export function LaneChangesPanel({
       // `only: "staged"` — the whole point of staging file by file is that the
       // commit takes the index as it stands, with no `add -A` sweeping the
       // rest of the tree in behind it.
-      await api.lanes.gitAction(lane, "commit", { message: message.trim(), only: "staged" });
+      await api.lanes.gitAction(target, "commit", { message: message.trim(), only: "staged" });
       if (laneNow.current !== lane) return;
       setMessage("");
       refreshGit();
@@ -1055,7 +1062,13 @@ export function LaneChangesPanel({
       )}
       <div className="flex min-h-0 min-w-0 flex-1 flex-col">
         {!filesTab && (
-          <LaneGitHeader laneId={laneId} git={git} onChanged={rereadAll} onNewLane={onNewLane} />
+          <LaneGitHeader
+            laneId={laneId}
+            session={session}
+            git={git}
+            onChanged={rereadAll}
+            onNewLane={onNewLane}
+          />
         )}
         {/* ONE wrapping row: where you are (mode) then how you are looking at it
           (range, layout, context, whole file), refresh last. Each group is
@@ -1430,6 +1443,7 @@ export function LaneChangesPanel({
           ) : mode === "file" && range === "work" && current?.conflicted && !rawEdit && openFile ? (
             <LaneConflictView
               laneId={laneId}
+              session={session}
               path={openFile}
               onResolved={() => {
                 refreshGit();