fix(review): enforce repo gate for e2e generation

[JSONbored]

Motivation

• Close a security gap where the E2E test generator only checked the global e2eTests kill-switch and not the per-repo converged-feature decision, which could let private PR diffs be sent to an AI provider and consume BYOK/shared quota.

Description

• Add an explicit per-repo gate by calling convergedFeatureActive(env, input.repoFullName, "e2eTests") early in runGittensoryE2eTestGeneration and return a disabled result when it is not active (file: src/services/ai-e2e-test-gen.ts).
• Update the generator header comment to document that generation requires both the global kill-switch and the repo manifest/allowlist activation.
• Add test helpers and manifest seeding (cacheEmptyManifest, enabledEnvWithCachedManifest) and import upsertRepoFocusManifest so tests can exercise the repo manifest path, and add regression tests that assert an unallowlisted repo is disabled and a repo-specific features.e2eTests: true opt-in enables generation (file: test/unit/ai-e2e-test-gen.test.ts).
• Adjust existing unit tests to seed cached manifests where needed so the per-repo resolver behavior is covered.

Testing

• Ran npx vitest run test/unit/ai-e2e-test-gen.test.ts; unit tests passed (41 tests).
• Ran npm run typecheck; TypeScript typecheck passed.
• Ran coverage with npm run test:coverage -- test/unit/ai-e2e-test-gen.test.ts; tests completed successfully but coverage remapping failed with TypeError: jsTokens is not a function during V8→lcov conversion.
• Ran npm audit --audit-level=moderate; the audit step failed with a 403 Forbidden from the npm registry and could not complete.

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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 (15bfdce).
⚠️ Report is 13 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4386   +/-   ##
=======================================
  Coverage   93.95%   93.95%           
=======================================
  Files         400      400           
  Lines       36817    36819    +2     
  Branches    13451    13452    +1     
=======================================
+ Hits        34592    34594    +2     
  Misses       1569     1569           
  Partials      656      656           

Files with missing lines	Coverage Δ
src/services/ai-e2e-test-gen.ts	100.00% <100.00%> (ø)

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