test(BRIDGE-WP-0003): add sentinel self-validation for meta-test + MCP section in README

- Add test_meta_test_catches_missing_mode_gap() — validates Goal #4:
  injects _test_sentinel capability (cli+mcp required), provides only
  a cli mock item, asserts collect_capability_coverage reports the mcp gap.
  Proves the cross-mode gap-detection mechanism is functional.

- Add MCP INTEGRATION section to README.txt (T14 requirement): documents
  project-scope .mcp.json, user-scope registration script, skill, and
  direct server invocation.

189 tests, 0 lint errors.

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

README.txt

@@ -181,6 +181,34 @@ bridge_reconnecting, health_check_failed, health_check_recovered,
 bridge_stopped
 
 
+MCP INTEGRATION
+---------------
+
+OpsBridge exposes its capabilities as a FastMCP server so Claude Code agents
+can call bridge_up(), bridge_status(), catalog_list_targets(), etc. as
+first-class MCP tools — no Bash required, structured JSON in/out.
+
+Available tools:  bridge_up, bridge_down, bridge_restart, bridge_status,
+                  bridge_logs, catalog_list_targets, catalog_show_target,
+                  catalog_list_domains, catalog_validate, catalog_show_bridge
+
+Available resources:  bridge://status, catalog://domains, catalog://targets
+
+Project-scope (auto, inside ops-bridge/):
+  Already configured in .mcp.json. Claude Code sessions inside this repo
+  see the tools automatically.
+
+User-scope (machine-global, any repo):
+  python scripts/register_mcp.py
+
+Human operator skill:
+  /bridge-status  —  natural-language tunnel health summary
+  (skill file: ~/.claude/plugins/ops-bridge/bridge-status.md)
+
+Run the server directly (for debugging):
+  uv run python src/bridge/mcp_server/server.py
+
+
 DEVELOPMENT
 -----------