feat(ui): re-analyze CTA for legacy Session Musician runs

[slittycode]

Successor to #24 (auto-closed when its base branch claude/thirsty-easley-faeaea was deleted after PR #22 merged). Branch rebased onto main with PR #28's per-stem-confidence changes already present; no conflicts surfaced.

Why

When a cached run shows up with transcriptionMethod: 'basic-pitch' (or any non-torchcrepe method), the Stem note draft block enters its legacy render state and shows the existing notice "Re-analyze for current stem-aware quality. The notes below are kept for archival." But PR #22 left it at just words — this adds the actual button.

Behaviour

• Block A renders a "Re-analyze with stem-aware pipeline" button only in the legacy render state AND only when App passes a callback (a source File is loaded and no analysis is currently in flight).
• Clicking the button calls back through <SessionMusicianPanel> → <AnalysisResults> → App.tsx, which fires handleStartAnalysis({ pitchNoteRequested: true }). The File state is retained in App across analyses, so no re-upload is required.
• The STEM PITCH/NOTE TRANSLATION toggle is also updated to reflect the override so subsequent manual Run Analysis clicks behave consistently.

Investigation: does the backend support artifact reuse?

analysis_runtime.create_run stores the artifact bytes anew on every call — there's no API to reference a prior artifact ID. Because audioFile: File is retained in App state, the cleanest path is to re-POST the same File. No backend changes needed.

Tests

• 5 new Vitest cases: legacy + callback → button renders, legacy + no callback → no button, stem-aware → no button, full-mix-fallback → no button, ran-with-no-result / requested-but-unavailable → no button.
• Smoke test stubs transcriptionMethod: 'basic-pitch', clicks the CTA, asserts a second POST to /api/analysis-runs fires with pitch_note_mode=stem_notes.

47 smoke tests pass (1 skipped).

🤖 Generated with Claude Code

[slittycode]

Verdict: APPROVE

Summary

Adds a "Re-analyze with stem-aware pipeline" CTA button to NoteDraftBlock when it's in the legacy render state — wired through a callback chain from App.tsx down via AnalysisResults and SessionMusicianPanel. The handleStartAnalysis override pattern correctly captures the active pitch-note setting before the render cycle, then syncs the toggle state for consistency. Tests pass: 354/354 unit, 47/47 smoke (1 skipped per the description). No Phase 1 measurements are touched or re-derived anywhere in the diff.

Findings

None.

Test results

354 passed / 0 failed across 36 test files. The five new unit tests in sessionMusicianPanel.test.ts cover the expected render-state matrix cleanly (legacy+callback, legacy+no-callback, stem-aware, full-mix-fallback, ran-with-no-result/requested-but-unavailable). The smoke test correctly exercises the POST-fires-with-pitch_note_mode=stem_notes path.

One thing worth knowing: the smoke fixture at run_smoke_reanalyze_1 has both transcriptionMethod: 'basic-pitch' and fullMixFallback: true, which at first glance looks like it should hit full-mix-fallback render state and break the data-render-state="legacy" assertion. It doesn't — renderState.ts Rule 5 explicitly documents that legacy method wins over the fallback flag, and the unit test for full-mix-fallback uses a torchcrepe baseline to confirm the precedence. The fixture is fine.

Phase boundary check

Clean. No Phase 1 output is mutated or re-derived. Callback flows from App → AnalysisResults → SessionMusicianPanel → NoteDraftBlock are pure prop-threading with no access to measurement state.

---

Generated by Claude Code