feat(repos): multi-machine path support via host_paths

Adds a JSONB column `host_paths` to managed_repos mapping
hostname → absolute local path. Fixes the consistency-checker
failure when the same repo lives at different paths on different
machines (e.g. /home/worsch/marki-docx on the workstation vs
/home/tegwick/marki-docx on custodiancore).

Changes:
- Migration g4b5c6d7e8f9: adds host_paths JSONB (default {})
- Model: host_paths Mapped[dict] column
- Schemas: host_paths in RepoRead; new RepoPathRegister schema
- Router: POST /repos/{slug}/paths/ — merges one host entry
- consistency_check.py: resolve_repo_path() prefers host_paths
  [hostname] over local_path; --repo-path CLI override added
- MCP: update_repo_path(slug, path, host?) tool
- Makefile: register-path target; REPO_PATH passthrough on
  check-consistency and fix-consistency targets
- TOOLS.md: documents update_repo_path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mcp_server/TOOLS.md

@@ -104,6 +104,7 @@ Domains are now first-class DB entities. Use `list_domains()` to discover availa
 | `archive_domain(slug)` | `slug` | Soft-delete; fails if active topics exist. |
 | `list_domain_repos(domain_slug)` | `domain_slug` | List repos registered under a domain. |
 | `register_repo(domain_slug, name, ...)` | `slug?`; `local_path?`; `remote_url?` | Register a git repo under a domain. |
+| `update_repo_path(repo_slug, path, host?)` | `repo_slug`: e.g. `"marki-docx"`; `path`: absolute local path; `host`: defaults to current hostname | Register this machine's local path for a repo. Use when the same repo lives at different paths on different machines (e.g. `/home/worsch/…` vs `/home/tegwick/…`). The consistency checker prefers this over `local_path`. |
 
 ---