feat(edit-history): edit history panel for local claude sessions

Part 1 of #643 (local sessions only; remote follows as its own PR). An
opt-in, per-device header button opens a panel with the active session's
edits, newest first: every Edit/Write/MultiEdit/NotebookEdit of the main
agent and its subagents with its diff, plus images a Bash call rendered or
the agent sent. Remote, Docker and non-claude sessions answer `unsupported`.

- Reads only on request: `?sync=1` when the panel opens; while it is open on
  that session it re-reads after an edit-capable `transcript:tool_end` or a
  `transcript:complete` from the existing transcript watcher. No hook, timer,
  second watcher or new SSE event; a wiring guard pins it.
- Main transcript: the path the transcript watcher follows (hook-reported),
  else `<id>.jsonl` under the session's own CLAUDE_CONFIG_DIR override or
  the server's config dir. A config dir set outside Codeman is found with
  the next hook; until then the panel says so.
- Store: dataPath('edit-history')/<id>.json, 0600 via tmp+rename, capped at
  500 entries and 4 MiB of diff text per session, deleted with the session,
  blocked in isSensitivePath, never fed to /api/search. Every route goes
  through findSessionOrFail with req.
- Images only through existing file surfaces: file-raw inside the
  workspace, the attachment route with notify:false outside it.
- textContent rendering, bounded byte-offset reads, marker-class header
  button, hidden on phones (locked in the mobile policy test).

Docs: Working-With-Files, Settings-Reference, architecture invariants, API
reference, CLAUDE.md key pattern.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/session.ts

@@ -2610,7 +2610,7 @@ export class Session extends EventEmitter {
     if (entry?.launch.chain !== 'fallback') return options;
 
     const resumeIdPattern = entry.launch.params?.resumeId;
-    const configDir = this._claudeConfigDir();
+    const configDir = this.claudeConfigDir();
     const chainTail = this._claudeSessionChain[this._claudeSessionChain.length - 1];
     const candidates = [chainTail, options.resumeSessionId, this.id].filter((v): v is string => !!v);
     for (const candidate of candidates) {
@@ -2632,8 +2632,11 @@ export class Session extends EventEmitter {
     return options;
   }
 
-  /** The session's Claude config dir when it has been relocated (#255), else undefined. */
-  private _claudeConfigDir(): string | undefined {
+  /**
+   * The session's Claude config dir when it has been relocated (#255), else undefined.
+   * Public for the edit history reader, which looks for the transcript there.
+   */
+  claudeConfigDir(): string | undefined {
     // Trimmed like `claudeProjectsDir()` trims the process-wide override: the
     // envOverrides schema validates keys only, and a whitespace-only value would
     // otherwise resolve to a relative path and read "no transcript" for everything.