fix(mcp): bound predict-gate changedPaths

[JSONbored]

Motivation

• Prevent unbounded caller-controlled path strings in the MCP gittensory_predict_gate input from driving large allocations and CPU during path-glob matching by applying the same per-path metadata size cap used elsewhere.

Description

• Constrain changedPaths elements in the MCP predictGateShape to PREFLIGHT_LIMITS.changedFileChars (using z.string().min(1).max(PREFLIGHT_LIMITS.changedFileChars)), keeping the existing array cap of 500.
• Add a regression unit test that submits an oversized changedPaths entry to gittensory_predict_gate and asserts the call is rejected before prediction processing.

Testing

• Ran the focused unit test file with npx vitest run test/unit/mcp-predict-gate.test.ts, and all tests in that file passed.
• Ran git diff --check and npm run typecheck and they succeeded (no typing or diff issues).
• Ran the full local gate with npm run test:ci; the targeted change passed, but the full suite aborted on unrelated long-running coverage remap work with TypeError: jsTokens is not a function and therefore did not complete end-to-end.
• npm audit --audit-level=moderate could not complete due to a registry audit endpoint error (network/403) 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 95.39%. Comparing base (a356441) to head (aae81c7).
⚠️ Report is 12 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1438   +/-   ##
=======================================
  Coverage   95.39%   95.39%           
=======================================
  Files         193      193           
  Lines       20929    20929           
  Branches     7564     7564           
=======================================
  Hits        19966    19966           
  Misses        383      383           
  Partials      580      580           

Files with missing lines	Coverage Δ
src/mcp/server.ts	95.56% <ø> (ø)

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