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/LaneConflictView.tsx

@@ -15,7 +15,7 @@
 import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { ChevronDown, ChevronUp } from "lucide-react";
-import { api } from "../../lib/api";
+import { api, gitTarget } from "../../lib/api";
 import {
   applyChoices,
   parseConflicts,
@@ -37,11 +37,14 @@ function Lines({ lines, className = "" }: { lines: string[]; className?: string
 
 export function LaneConflictView({
   laneId,
+  session,
   path,
   onResolved,
   onEdit,
 }: {
   laneId: number;
+  /** Work in that session's own worktree (see `gitTarget`). */
+  session?: string;
   path: string;
   /** The file left the conflict (resolved, or a whole side taken). */
   onResolved: () => void;
@@ -62,7 +65,7 @@ export function LaneConflictView({
     setChoices([]);
     setError(null);
     api.lanes
-      .gitFile(laneId, path, "work")
+      .gitFile(gitTarget(laneId, session), path, "work")
       .then((r) => {
         if (!live) return;
         setFile(
@@ -75,7 +78,7 @@ export function LaneConflictView({
     return () => {
       live = false;
     };
-  }, [laneId, path]);
+  }, [laneId, session, path]);
 
   const parts: ConflictPart[] | null = file?.usable ? parseConflicts(file.lines) : null;
   const total = parts ? parts.filter((p) => p.kind === "conflict").length : 0;
@@ -98,11 +101,16 @@ export function LaneConflictView({
   const save = () =>
     run(async () => {
       if (!parts || !file?.sha) return;
-      await api.lanes.gitSaveFile(laneId, path, applyChoices(parts, choices).join("\n"), file.sha);
-      await api.lanes.gitAction(laneId, "resolve", { path, side: "done" });
+      await api.lanes.gitSaveFile(
+        gitTarget(laneId, session),
+        path,
+        applyChoices(parts, choices).join("\n"),
+        file.sha
+      );
+      await api.lanes.gitAction(gitTarget(laneId, session), "resolve", { path, side: "done" });
     });
   const takeAll = (side: "ours" | "theirs") =>
-    run(() => api.lanes.gitAction(laneId, "resolve", { path, side }));
+    run(() => api.lanes.gitAction(gitTarget(laneId, session), "resolve", { path, side }));
 
   const choose = (i: number, c: ConflictChoice | undefined) =>
     setChoices((prev) => {