refactor(vault): Phase 3 — metadata convergence

- Backfill `created` frontmatter on 266 active notes (git date or mtime)
- Normalize `status` to 4 values: draft/active/done/archived (11 notes)
  - Active/进行中/needs-review → active
  - archive → archived
  - 待执行/conditional → draft
  - 完成/accepted → done
- Declare clipper boundary: 04_Archive/Inbox-Clippings/** exempt from migration
- Update depth rule: max 3 → max 4 levels (new notes only)
- Add metadata-converge.mjs script for reproducibility

00_Inbox/Untitled.md

@@ -5,7 +5,7 @@ tags:
   - inbox
   - security
   - credentials
-status: needs-review
+status: active
 ---
 
 # 2026-03-16