refactor(self-mod): drop request_rebuild — approvals now bundle rebuild+restart

install_packages and add_mcp_server already did the right thing on approve
(install auto-rebuilt+killed, add_mcp_server just killed), so request_rebuild
was redundant plumbing agents sometimes called after an install — wasting an
admin approval round-trip. Delete it end-to-end:

- container/agent-runner/src/mcp-tools/self-mod.ts: remove requestRebuild
  tool + registration; update install_packages description.
- src/modules/self-mod/{request,apply,index}.ts: drop handleRequestRebuild
  + applyRequestRebuild + registrations; rewrite the rebuild-failed notify
  to point admins at retrying install_packages instead.
- src/modules/{approvals,self-mod}/{agent,project}.md and skill/self-
  customize/SKILL.md: scrub agent-facing references; clarify that
  add_mcp_server needs no rebuild (bun runs TS directly).
- docs/{module-contract,architecture-diagram,checklist,db-central,shared-
  source,v1-vs-v2/*}.md, CLAUDE.md, pending-approvals migration comment,
  approvals/index.ts docstring, REFACTOR.md: trailing references.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/shared-source.md

@@ -73,7 +73,7 @@ What remains per-group (unchanged):
 
 ### Self-modification
 
-Existing config-level self-mod tools (`install_packages`, `add_mcp_server`, `request_rebuild`) mutate `container.json` and per-group images, not source. Unchanged — stays per-group.
+Existing config-level self-mod tools (`install_packages`, `add_mcp_server`) mutate `container.json` and per-group images, not source. Unchanged — stays per-group.
 
 Source-level self-modification (not yet implemented) uses staging: edits happen against a copy of `container/agent-runner/src/`, reviewed and swapped in on approval. Owner can also edit source directly.