journal log: preflight the transcriber toolchain at record-start, not after recording

[claude]

🤖 Agent-Generated PR

Closes #82
Agent Used: Claude Code
Complexity: medium

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Summary

journal log's mic-toggle/hotkey flow preflighted ffmpeg before recording but only discovered a missing whisper.cpp binary or model file after the recording finished (inside Transcribe()), wasting the recording. This adds a transcriber preflight to the record-start path, mirroring the existing ffmpeg preflight.

Implementation Notes

• Added internal/log.CheckAvailable(modelDir, model string) error, which performs the same two checks WhisperCPP.Transcribe does (model file os.Stat, binary findWhisperBin lookup) but without running transcription. Transcribe itself is untouched to avoid any risk to the existing transcription path.
• Added an injectable checkTranscriberAvailable var in cmd/log.go, mirroring the existing checkFfmpegAvailable pattern, so tests never depend on a real whisper.cpp install/model.
• Wired it into runLogStartRecording right after the ffmpeg check and before the recorder is spawned / lockfile is written.
• On failure it returns the same actionable error (run \journal models pull` / whisper.cpp install hint) and additionally sends a desktop notification (✕ journal log failed`) — the ffmpeg preflight's existing behavior (terminal-only, no notification) is left unchanged, per the issue's acceptance criteria.
• The direct journal log <audio.wav> path is untouched — it already surfaces transcription errors inline.

Changes

• internal/log/transcribe.go: add CheckAvailable.
• cmd/log.go: add checkTranscriberAvailable var, call it in runLogStartRecording.
• internal/log/transcribe_test.go: table test for CheckAvailable covering present / missing-binary / missing-model.
• cmd/log_test.go: add stubTranscriberAvailable helper, wire it into existing start/toggle tests, and add new tests covering the fail-fast behavior (no spawn, no lockfile, notification sent) and the pass-through (available) case.

Testing

Automated:

• Unit tests added/updated
• Integration tests added/updated
• All existing tests pass

Manual testing performed:

• Ran make fmt vet, go build ./..., and go test -p 1 ./... locally — all green.
• golangci-lint isn't available in this environment; CI will run it on the PR.

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Review Checklist

Correctness

• Code actually solves the issue
• Acceptance criteria are met
• Edge cases handled

Code Quality

• Follows existing codebase patterns
• Follows project coding standards
• Naming conventions consistent
• No unnecessary complexity
• Comments where needed (but code is self-documenting)

Security

• Input validation present
• No exposed secrets or credentials
• Data properly sanitized/escaped
• Authentication/authorization checks where needed

Performance

• No obvious N+1 queries
• Reasonable algorithmic complexity
• Caching used where appropriate
• No blocking operations in request lifecycle

Tests

• Tests actually test behavior (not just coverage)
• Edge cases covered
• Failure modes tested

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Reviewer Notes

Out of scope per the issue: bundling whisper.cpp or auto-pulling models — not touched.

[claude]

Retro: no durable lesson (merged clean / one-off).