feat(governance): add prompt versioning, rollback --list, and state backup

- governance/index.js: archive filenames now include ISO timestamp for
  deterministic sorting (<base>_<ts>_<hash>.md); write .meta.json sidecar
  on every archive with proposalId, author, reason, and archivedAt
- governance/index.js: add listPromptVersions(target) — returns archived
  versions for a prompt sorted newest-first with sidecar metadata surfaced
- cmd-rollback.mjs: add --list flag to list available versions without
  restoring (delegates to listPromptVersions)
- cli-parser.mjs: add --list and --output flags
- lib.mjs: pass list flag to cmdRollback; add backup command dispatch
- cmd-backup.mjs: new torch-lock backup command — snapshots
  .scheduler-memory/memory-store.json and scheduler run state to
  .torch/backups/<timestamp>/; supports --output override and --list
- docs/prompt-versioning.md: comprehensive guide to the full
  proposal → apply → list-versions → rollback workflow, state backup
  and restore procedure, and storage location reference
- test/governance.test.mjs: 7 scenario-based tests (SCN-proposal-create,
  SCN-proposal-list, SCN-proposal-reject, SCN-archive-naming,
  SCN-version-list, SCN-rollback-latest, SCN-rollback-hash)

https://claude.ai/code/session_01Ndq2D72Kp77BYo4owD63uY

src/cmd-rollback.mjs

@@ -1,12 +1,23 @@
-import { rollbackPrompt } from './services/governance/index.js';
+import { rollbackPrompt, listPromptVersions } from './services/governance/index.js';
 import { ExitError } from './errors.mjs';
 
-export async function cmdRollback(target, strategy) {
+export async function cmdRollback(target, strategy, { list = false } = {}) {
   if (!target) {
-    console.error('Usage: torch-lock rollback --target <path> [--strategy <hash|latest>]');
+    console.error('Usage: torch-lock rollback --target <path> [--strategy <hash|latest>] [--list]');
     throw new ExitError(1, 'Missing target');
   }
 
+  if (list) {
+    try {
+      const versions = await listPromptVersions(target);
+      console.log(JSON.stringify(versions, null, 2));
+    } catch (e) {
+      console.error(`Failed to list versions: ${e.message}`);
+      throw new ExitError(1, 'List versions failed');
+    }
+    return;
+  }
+
   const effectiveStrategy = strategy || 'latest';
 
   try {