fix: use _resetForTesting() consistently to prevent flaky tests

[G-hoon]

Summary

• Fix flaky mainSessionID tests caused by state pollution in parallel test execution
• Use _resetForTesting() consistently across all test files that modify session state

Changes

• src/hooks/keyword-detector/index.test.ts: Replace setMainSession(undefined) with _resetForTesting() in beforeEach/afterEach hooks
• src/features/claude-code-session-state/state.test.ts: Un-skip the previously flaky test

Root Cause

Some test files were using setMainSession(undefined) which only clears _mainSessionID, but _resetForTesting() also clears subagentSessions. This inconsistency caused state pollution when tests run in parallel.

Testing

bun test src/features/claude-code-session-state/state.test.ts src/hooks/keyword-detector/index.test.ts

Ran 5 consecutive test runs with 0 failures.

Fixes #848

---

Summary by cubic

Consistently reset session state in tests using _resetForTesting() to stop flaky mainSessionID failures and prevent state leaks across parallel runs. Fixes #848.

• Bug Fixes
  • Replace setMainSession(undefined) with _resetForTesting() in keyword-detector tests; add cleanup in afterEach.
  • Unskip the “should return undefined when not set” test in claude-code-session-state.

^{Written for commit 0d10bcd. Summary will update on new commits.}

[github-actions]

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[G-hoon]

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[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.