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/WorkspaceHome.tsx

@@ -12,6 +12,7 @@
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
+import { Checkbox } from "../Checkbox";
 import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useNavigate } from "react-router-dom";
@@ -19,6 +20,7 @@ import {
   ArchiveRestore,
   FileText,
   Folder,
+  GitBranch,
   MoreHorizontal,
   Pencil,
   Play,
@@ -41,7 +43,13 @@ import { Select } from "../Select";
 import { MarkdownPreview } from "../MarkdownPreview";
 import { WorkspaceRowMenu, type WorkspaceMenuAction } from "./WorkspaceRowMenu";
 import { workspaceName } from "./WorkspaceRow";
-import { liveRunFor, SessionFold, sessionDot, useSessionPage } from "./WorkspaceSessionList";
+import {
+  liveRunFor,
+  SessionFold,
+  sessionDot,
+  sessionWorktreeName,
+  useSessionPage,
+} from "./WorkspaceSessionList";
 
 /** The tmux session a pane slot of a lane owns (server/lib/pty-run.js). */
 export function paneRunId(laneId: number, slot: number): string {
@@ -96,6 +104,9 @@ function HomeBody({
   const [model, setModel] = useState(defaultModel);
   useEffect(() => setModel(defaultModel), [defaultModel]);
   const [mode, setMode] = useState<PermissionMode>("auto");
+  // Claude Desktop's worktree toggle: the new session gets a git worktree of
+  // its own (`claude --worktree`), made and cleaned up by Claude Code.
+  const [inWorktree, setInWorktree] = useState(false);
   const [starting, setStarting] = useState(false);
   const [error, setError] = useState<string | null>(null);
   const [liveRuns, setLiveRuns] = useState<RunHandle[]>([]);
@@ -219,6 +230,7 @@ function HomeBody({
         prompt: prompt.trim(),
         ...(model ? { model } : {}),
         ...(claude ? { permissionMode: mode } : {}),
+        ...(claude && inWorktree && project?.root ? { worktree: true } : {}),
       });
       setPrompt("");
       const runId = r.run_id ?? paneRunId(lane.id, slot);
@@ -344,6 +356,15 @@ function HomeBody({
                 />
               </div>
             )}
+            {claude && project?.root && (
+              <Checkbox
+                checked={inWorktree}
+                onChange={setInWorktree}
+                label={t("home.worktree")}
+                title={t("home.worktreeHint")}
+                className="ml-1"
+              />
+            )}
             <button
               type="button"
               data-testid="workspace-home-start"
@@ -382,6 +403,15 @@ function HomeBody({
                   <span className="min-w-0 flex-1 truncate text-sm text-fg-primary">
                     {s.name || s.id.slice(0, 8)}
                   </span>
+                  {sessionWorktreeName(lane, s) && (
+                    <span
+                      title={t("tree.worktreeSession", { name: sessionWorktreeName(lane, s) })}
+                      className="inline-flex shrink-0 items-center gap-1 font-mono text-[11px] text-fg-muted"
+                    >
+                      <GitBranch className="h-3 w-3" />
+                      {sessionWorktreeName(lane, s)}
+                    </span>
+                  )}
                   {!!s.cost && s.cost > 0 && (
                     <span className="shrink-0 text-xs tabular-nums text-fg-muted">
                       {fmtCost(s.cost)}