feat(mcp): add loopover_get_gate_config_effective MCP tool

[jsdevninja]

Summary

• Closes loopover_get_gate_config_effective has a REST route but no remote MCP tool or local stdio MCP tool #7800: loopover_get_gate_config_effective has a REST route (GET /v1/repos/:owner/:repo/gate-config/effective) but no MCP tool on either surface.
• Registers loopover_get_gate_config_effective as a remote MCP tool in src/mcp/server.ts, mirroring loopover_get_pr_reviewability's pattern: ownerRepoShape input, an output schema matching the REST route's exact response shape, the maintainer category, and the same canAccessRepo precedent the other maintainer read tools already use.
• Registers the same tool as a local stdio CLI proxy in packages/loopover-mcp/bin/loopover-mcp.ts, proxying to the existing REST route via apiGet. No new REST route and no new human-typable CLI verb, per the issue.
• Bumps the pinned MCP tool-count invariant (test/unit/mcp-tool-rename-aliases.test.ts) from 80 to 81.

Test plan

• npm run typecheck
• npm run build --workspace @loopover/engine && npm run build --workspace @loopover/mcp
• New tests: test/unit/mcp-gate-config-effective.test.ts (remote MCP tool: no-override, live override + soaking shadow, confidence-floor-only override, forbidden-repo) and test/unit/mcp-cli-gate-config-effective.test.ts (stdio CLI proxy: registers in tool list, proxies to the REST path, surfaces shadowPending without leaking the shadow's queued recommendation)
• Added a fixture route for gate-config/effective in test/unit/support/mcp-cli-harness.ts
• Updated test/unit/mcp-tool-rename-aliases.test.ts's pinned tool count (80 → 81)
• Full targeted run green: mcp-cli-gate-config-effective, mcp-gate-config-effective, mcp-tool-categories, mcp-output-schemas, mcp-cli-maintain-tools, mcp-cli-tools-search, mcp-tool-rename-aliases, mcp-cli-pr-reviewability (82 tests, all passing)

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.33%. Comparing base (2364ad4) to head (e7a83a8).

Files with missing lines	Patch %	Lines
packages/loopover-mcp/bin/loopover-mcp.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #7900       +/-   ##
===========================================
- Coverage   91.40%   81.33%   -10.07%     
===========================================
  Files         730       90      -640     
  Lines       74789    24364    -50425     
  Branches    22822     4690    -18132     
===========================================
- Hits        68358    19816    -48542     
+ Misses       5389     4348     -1041     
+ Partials     1042      200      -842     

Flag	Coverage Δ
shard-1	15.14% <11.76%> (-42.84%)	⬇️
shard-2	12.63% <11.76%> (-38.60%)	⬇️
shard-3	24.76% <82.35%> (-26.39%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/mcp/server.ts	96.50% <100.00%> (+0.04%)	⬆️
packages/loopover-mcp/bin/loopover-mcp.ts	0.00% <0.00%> (ø)

... and 640 files with indirect coverage changes

[loopover-orb]

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