fix: make logger rotation tests deterministic

[ChrisRomp]

Replace setTimeout sleeps in logger rotation tests with an awaitable waitForRotation() function. The logger now tracks its rotation promise internally; tests await it instead of guessing timing.

Result: Logger test suite runs in ~9ms instead of ~1500ms. No more timing-dependent flakiness.

Closes #171

[Copilot]

Pull request overview

This PR makes the logger rotation tests deterministic by removing fixed setTimeout sleeps and replacing them with an awaitable mechanism tied to the logger’s actual rotation work. It fits the codebase by improving the reliability and speed of the Vitest suite around src/logger.ts’s self-managed log rotation.

Changes:

• Track the in-progress rotation via an internal _rotationPromise updated when rotation starts.
• Expose a testing-oriented waitForRotation() helper so tests can await completion rather than sleep.
• Update src/logger.test.ts to use await waitForRotation() at rotation points, reducing runtime and flakiness.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/logger.ts	Tracks rotation with _rotationPromise and exports waitForRotation() to await rotation completion (used by tests).
src/logger.test.ts	Replaces timing-based sleeps with waitForRotation() to make rotation assertions deterministic and faster.

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