chore: remove backend code nothing references

Found with knip (exports, types, class members) and confirmed by a text
search of src, test, scripts and packages before each removal.

- Per-CLI get<Cli>NotFoundMessage() (nine of them) with their message
  constants: missingCliMessage() builds that text from the registry now.
- Registry leftovers: renderCliCommand, asCliId, cliIds, isCliRunnable,
  createCliResolverForTest, profileExists, and two name lists that only
  repeated schema enums.
- A task-description cache in Session that was written on every chunk of
  terminal output (one regex pass per line) and never read since the
  subagent watcher takes descriptions from transcripts. The cache module,
  its pattern and both parse methods go with it.
- Session.parentAgentId / childAgentIds: never set by anything, so the two
  optional SessionState fields were never on the wire.
- Unreferenced methods on TmuxManager (pipe-pane pair, syncMouseMode),
  RespawnController, StateStore.recoverFromBackup (load() already falls
  back to the .bak file), TeamWatcher, SseStreamManager and the AI
  checkers' getErrorVerdict.
- updateCaseEnvVars: the settings.local.json env path that envOverrides
  replaced.
- Re-exports in the utils, cli-registry, routes and prompts barrels that
  no importer used, and unused test helpers (MockStateStore, the mobile
  throttle helpers and others).

Eight mobile tests imported the WebServer type from a path that does not
exist (../src instead of ../../src); type-only, so nothing failed.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

src/tmux-manager.ts

@@ -4451,21 +4451,6 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     }
   }
 
-  /**
-   * Sync mouse mode based on pane count: enable if split (>1 pane), disable if single.
-   * Called by TeamWatcher when teammates spawn/despawn panes.
-   * Uses `tmux list-panes` for bulletproof detection — counts actual panes, not config.
-   */
-  async syncMouseMode(muxName: string): Promise<boolean> {
-    if (IS_TEST_MODE) return true;
-    const panes = await this.listPanes(muxName);
-    if (panes.length > 1) {
-      return this.enableMouseMode(muxName);
-    } else {
-      return this.disableMouseMode(muxName);
-    }
-  }
-
   /**
    * List all panes in a tmux session.
    * Returns structured info for each pane.
@@ -4782,67 +4767,6 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     }
   }
 
-  /**
-   * Start piping pane output to a file using tmux pipe-pane.
-   * Only pipes output direction (-O) to avoid echoing input.
-   */
-  startPipePane(muxName: string, paneTarget: string, outputFile: string): boolean {
-    if (IS_TEST_MODE) return true;
-    if (!isValidMuxName(muxName)) {
-      console.error('[TmuxManager] Invalid session name in startPipePane:', muxName);
-      return false;
-    }
-    if (!SAFE_PANE_TARGET_PATTERN.test(paneTarget)) {
-      console.error('[TmuxManager] Invalid pane target:', paneTarget);
-      return false;
-    }
-    if (!isValidPath(outputFile)) {
-      console.error('[TmuxManager] Invalid output file path:', outputFile);
-      return false;
-    }
-
-    const target = paneTarget.startsWith('%') ? `${muxName}.${paneTarget}` : `${muxName}.%${paneTarget}`;
-
-    try {
-      execSync(`${this.tmux()} pipe-pane -O -t ${shellescape(target)} ${shellescape('cat >> ' + outputFile)}`, {
-        encoding: 'utf-8',
-        timeout: EXEC_TIMEOUT_MS,
-      });
-      return true;
-    } catch (err) {
-      console.error('[TmuxManager] Failed to start pipe-pane:', err);
-      return false;
-    }
-  }
-
-  /**
-   * Stop piping pane output (calling pipe-pane with no command stops piping).
-   */
-  stopPipePane(muxName: string, paneTarget: string): boolean {
-    if (IS_TEST_MODE) return true;
-    if (!isValidMuxName(muxName)) {
-      console.error('[TmuxManager] Invalid session name in stopPipePane:', muxName);
-      return false;
-    }
-    if (!SAFE_PANE_TARGET_PATTERN.test(paneTarget)) {
-      console.error('[TmuxManager] Invalid pane target:', paneTarget);
-      return false;
-    }
-
-    const target = paneTarget.startsWith('%') ? `${muxName}.${paneTarget}` : `${muxName}.%${paneTarget}`;
-
-    try {
-      execSync(`${this.tmux()} pipe-pane -t ${shellescape(target)}`, {
-        encoding: 'utf-8',
-        timeout: EXEC_TIMEOUT_MS,
-      });
-      return true;
-    } catch (err) {
-      console.error('[TmuxManager] Failed to stop pipe-pane:', err);
-      return false;
-    }
-  }
-
   getAttachCommand(): string {
     return 'tmux';
   }