fix(files): list the git worktree an agent moved into (#765)

Claude Code's EnterWorktree moves the running process into
<repo>/.claude/worktrees/<name>, while Session.workingDir stays on the main
checkout. The Files panel kept walking workingDir, so it listed a tree the
agent had left.

paneCwd already follows the move, measured on Claude Code 2.1.318 in both
directions, so nothing new has to track the agent. It also follows every cd
in a shell, so a new SessionState.liveWorktree narrows it to a linked
worktree, read from the .git file without starting git.

Only a folder strictly below workingDir is ever an answer, and the listing
only starts there: returned paths stay relative to workingDir, so the
preview, raw and edit routes are unchanged and confinement does not widen.
A worktree outside the session folder stays unfollowed.

The panel asks with root=live, shows a strip naming the worktree with a
switch to the session folder, and follows the agent in and out while open.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/session.ts

@@ -73,6 +73,7 @@ import type { GitFetchStatus } from './git-fetch.js';
 import { resolveAndClaimOmpSessionId } from './utils/omp-session-resolver.js';
 import { claudeTranscriptExists } from './utils/claude-transcript.js';
 import { probePathKind } from './utils/bounded-path-probe.js';
+import type { LiveWorktree } from './live-worktree.js';
 import { PATH_PROBE_TIMEOUT_MS, WORKSPACE_REALPATH_RETRY_MS } from './config/path-probe.js';
 import { matchesPattern } from './config/cli-registry/patterns.js';
 import { probeDockerCliVersion } from './docker-hosts.js';
@@ -766,6 +767,8 @@ export class Session extends EventEmitter {
    * serialized by toState() but never restored by the constructor.
    */
   private _paneCwd: string | undefined;
+  /** See {@link liveWorktree}. */
+  private _liveWorktree: LiveWorktree | undefined;
   /**
    * `workingDir` with symlinks resolved, so a pane reading (tmux reads the
    * process cwd, always the resolved path) can be put back into `workingDir`'s
@@ -1576,6 +1579,22 @@ export class Session extends EventEmitter {
     return true;
   }
 
+  /**
+   * The linked git worktree inside `workingDir` that {@link paneCwd} is in, when there is one
+   * (`live-worktree.ts`). The Files panel lists it instead of the main checkout. Runtime-only and
+   * never a confinement root, like `paneCwd`: it is always a folder the file routes already serve.
+   */
+  get liveWorktree(): LiveWorktree | undefined {
+    return this._liveWorktree;
+  }
+
+  /** Record the result of a worktree lookup. Returns whether it CHANGED, so the caller broadcasts only then. */
+  setLiveWorktree(next: LiveWorktree | undefined): boolean {
+    if (next?.path === this._liveWorktree?.path) return false;
+    this._liveWorktree = next;
+    return true;
+  }
+
   /** `workingDir` without a trailing separator (the root stays `/`). */
   private _workspaceSpelling(): string {
     return this.workingDir.length > 1 ? this.workingDir.replace(/\/+$/, '') : this.workingDir;
@@ -2300,6 +2319,7 @@ export class Session extends EventEmitter {
       status: this._status,
       workingDir: this.workingDir,
       paneCwd: this._paneCwd,
+      liveWorktree: this._liveWorktree,
       remote: this._remote,
       docker: this._docker,
       owner: this._owner,