test: cover stt transcription and redis helpers

[derogab]

Summary

Adds coverage for STT transcription paths and Redis helper behavior so regressions in message handling and storage parsing are easier to catch.

Changes

• Cover Cloudflare audio transcription, whisper.cpp voice transcription, and the no-STT fallback in message handling tests.
• Mock STT, file lookup, fetch, and filesystem checks needed for isolated transcription tests.
• Add Redis storage coverage for bounded reconnect retries, stored history parsing, and active chat ID extraction.

Test plan

• npm test

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Summary by cubic

Add tests for STT transcription flows (Cloudflare, whisper.cpp, and no-STT fallback) and Redis helpers to prevent regressions in message handling and storage parsing. Tests mock fetch, filesystem, and STT to isolate behavior; verify audio/voice file retrieval and transcription updates; and check bounded Redis reconnect retries, stored history parsing, and active chat ID extraction.

^{Written for commit d52a6a2. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}