refactor(vault): Phase 5 — single agent contract

- Rewrite AGENTS.md as single operations manual (PARA, permission table,
  frontmatter conventions, safety rules, code style)
- Root CLAUDE.md = one-line pointer to AGENTS.md
- Delete 13 stub CLAUDE.md files across vault directories
- Delete .claude/project-instructions.md + .claude/memory/instructions/
  (content merged into AGENTS.md)
- .claude/settings.json: deny plugin data.json + 04_Archive + git push;
  ask on .obsidian/** edits; remove SessionStart hook (claudesidian welcome)
- Delete 3 upstream commands (init-bootstrap, install-claudesidian, upgrade)
- Add risk/writes metadata to 14 remaining commands
- Rewrite README.md (remove all claudesidian content)
- package.json: name → my-vault, remove check-updates/firecrawl scripts

.claude/commands/pull-request.md

@@ -1,4 +1,6 @@
 # Pull Request Command
+risk: high
+writes: git remote (push + PR)
 
 Creates a new feature branch, commits changes, pushes to GitHub, and opens a
 pull request - all in one command. Perfect for contributing features or fixes.