Variable hybrid clip length

[britle20]

Feature Spec

Related feature document: docs/features/19-variable-hybrid-clip-length.md

Goal

Allow hybrid clips to be 1, 2, or 4 bars long instead of fixed to 1 bar.

Context

Musical time is tick-based with PPQ 480. A 4/4 bar is 1920 ticks, so 2 bars is 3840 ticks and 4 bars is 7680 ticks.

Scope

Included:

• Clip length control for 1, 2, and 4 bars.
• Store clip length as lengthTicks.
• Derive drum and piano roll grids from clip length.
• Use clip length for PAT loop playback and arrangement default instance length.
• Safely handle shortening when events would fall outside the new length.

Excluded:

• Arbitrary clip lengths.
• Other time signatures.
• Per-clip tempo.
• Time-stretching.

Constraints

• Keep event positions in ticks.
• Preserve existing 1-bar behavior.
• Keep UI rendering separate from audio scheduling.

Done when

• 1, 2, and 4 bar clips can be edited and played.
• Events cannot silently exist outside the selected clip length.
• Existing 1-bar clips still work.

Verification

• npm run typecheck --if-present
• npm run lint --if-present
• npm run test --if-present
• npm run build --if-present

Notes

Planning created from the agentic workflow discuss-feature process.

[britle20]

Implemented by PR #54, merged into develop.