feat(player): add bounded rehearsal playback rates

[seonghobae]

Product gap

Add the next Issue #961 rehearsal-player slice on top of PR #1062: bounded, keyboard-accessible playback-speed control for real local audio.

Exact current identity

• Base branch: feat/rehearsal-player-first-section-loop
• Base HEAD: 82ec4538a4452d38253509d142e72c7faa9c6b28
• Current head: d99c9358b4c7bdcbf7d090c287b40d8104f97ade
• Parent: PR feat(player): play real audio section loops #1062

Product outcome

• Offers 0.75x, 1x, and 1.25x only through the single rehearsal transport state machine.
• Applies HTMLMediaElement.playbackRate to real media and reapplies it after source reloads.
• Enables preservesPitch when the runtime exposes the standard property.
• Announces the effective count-in tempo and preserves the elapsed fraction of the current beat when playback rate changes.
• Keeps section selection, pause/resume, count-in, and media-clock loop boundaries under the same transport state.
• Keeps playback fail-closed when no playable Tauri asset URL exists.

Stack scope

This shared stack branch currently contains the normal merges for PR #1066 (role-filtered loops), PR #1067 (keyboard section-cue navigation), and PR #1068 (manual cue-boundary corrections), followed by the playback-rate work. The current head above is the only head for hosted evidence.

Validation

• Focused transport/player tests: 39 passed.
• Full desktop test suite: 267 passed across 23 files; statements, branches, functions, and lines all 100%.
• Desktop typecheck and lint passed.
• Desktop Vite build passed; it reports the existing large-chunk warning.
• git diff --check passed.
• Hosted checks and robot review are being rerun for current head d99c9358b4c7bdcbf7d090c287b40d8104f97ade; prior-head results are not used as completion evidence.

Security Notes

• No new filesystem, URL, subprocess, IPC, WebView, or network boundary is introduced.
• Playback-rate input is accepted only from the fixed contract values; invalid runtime events leave state unchanged.
• Audio remains governed by PR feat(player): play real audio section loops #1062's scoped Tauri asset handling and selected-file validation. No path is logged.
• Playback-rate semantics follow the WHATWG HTML Standard media-element contract: playbackRate is effective speed and preservesPitch is enabled when supported: https://html.spec.whatwg.org/multipage/media.html
• The count-in timer is bounded to the admitted tempo/rate values and is cancelled when transport authority is revoked.

Acceptance ceiling

This slice does not claim role/stem isolation, real-device speaker-output acceptance, or Issue #770 known-take accuracy acceptance. Those remain separate product gaps.

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[devin-ai-integration]

Note

This report is out of date. Scroll down for Devin Review's latest report on this PR.

Devin Review found 5 new potential issues.

[devin-ai-integration]

Devin Review found 1 new potential issue.

[seonghobae]

Current-head follow-up for d99c935:\n\n- The count-in scheduler now owns one timer chain outside React commit batching, preserves elapsed beat progress across repeated 0.75x/1.25x changes, and cancels on transport authority loss.\n- Focused transport/player tests pass: 39.\n- Full desktop suite passes: 267 tests across 23 files, 100% statements/branches/functions/lines.\n- Typecheck and lint pass; Vite build passes with the existing large-chunk warning.\n- The current PR body documents the stack topology: #1066, #1067, and #1068 were normally merged into this shared branch before the playback-rate work, so the aggregate diff is intentional and no history was rewritten.\n- AGENTS.md now records that bounded pitch-preserving playback rate is delivered while stem playback remains a separate gap.\n\nHosted Devin review is pending for this exact head; no prior-head result is used as completion evidence.