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

.obsidian/plugins/claudian/CLAUDE.md

@@ -1,7 +0,0 @@
-<claude-mem-context>
-# Recent Activity
-
-<!-- This section is auto-generated by claude-mem. Edit content outside the tags. -->
-
-*No recent activity*
-</claude-mem-context>

.obsidian/plugins/obsidian-excalidraw-plugin/CLAUDE.md

@@ -1,7 +0,0 @@
-<claude-mem-context>
-# Recent Activity
-
-<!-- This section is auto-generated by claude-mem. Edit content outside the tags. -->
-
-*No recent activity*
-</claude-mem-context>