fix(mcp): validate open pr pressure input

[JSONbored]

Motivation

• The MCP tool gittensory_simulate_open_pr_pressure accepted unbounded/malformed queueHealth and roleContext (via z.unknown()), allowing authenticated callers to cause runtime TypeErrors or reflect large payloads into output.
• Tighten validation at the MCP boundary to prevent availability/resource-exhaustion and runtime crashes while keeping the simulator pure and read-only.

Description

• Replace permissive z.unknown() inputs with a bounded queueHealth schema (simulateOpenPrPressureQueueHealthSchema) that validates pressure level, numeric signal counts, limited findings and reasonable string lengths, and add SIMULATE_OPEN_PR_PRESSURE_MAX_COUNT to cap numeric fields.
• Validate roleContext minimally as an object with maintainerLane: boolean while using .passthrough() so the fuller engine context is preserved.
• Constrain repoFullName, generatedAt, and contributorOpenPrCount with length/number bounds to avoid oversized inputs.
• Add regression tests that exercise the MCP boundary rejecting roleContext: null, missing/ill-formed queueHealth.signals, and oversized/string queue counts so malformed inputs fail at schema validation instead of crashing or being reflected in output.

Testing

• Ran npm run build:miner and the build succeeded.
• Ran npx vitest run test/unit/mcp-simulate-open-pr-pressure.test.ts and all tests in that file passed.
• Ran npm run typecheck and TypeScript typecheck passed.
• Attempted coverage: npx vitest run --coverage test/unit/mcp-simulate-open-pr-pressure.test.ts the tests passed but coverage remapping failed with TypeError: jsTokens is not a function; a full npm run test:coverage run did not complete in this environment.
• npm audit --audit-level=moderate could not be completed due to the registry audit endpoint returning 403 Forbidden in this environment.

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Codex Task

[superagent-security]

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.95%. Comparing base (c823f9c) to head (e2f72b8).
⚠️ Report is 6 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4381   +/-   ##
=======================================
  Coverage   93.95%   93.95%           
=======================================
  Files         400      400           
  Lines       36817    36820    +3     
  Branches    13451    13451           
=======================================
+ Hits        34592    34595    +3     
  Misses       1569     1569           
  Partials      656      656           

Files with missing lines	Coverage Δ
src/mcp/server.ts	95.42% <100.00%> (+0.01%)	⬆️

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