feat(editor): track regions — the data model + migration (no UI yet)

[ChrisBeWithYou]

PR 1 of the track-regions arc — the data model + migration

Gives a track a region layer: regions[] is its audio/MIDI content as placeable blocks on the timeline. This first step is data-model only — no rendering, playback, or build changes — so the persistence round-trip is proven before any UI.

Output of a 7-seat design charrette (DAW / UX / host-compat / transcription / rhythm-meter / audio-engine / operability); the core design calls came back unanimous.

What's here

• src/region.js (new) — the region shape {id, startBeat, lenBeat, srcIn?, srcOut?, name?, muted?}, validation/dedupe/sort, the default full-span region, the default-is-null rule, and the beat-window membership predicate. A notation region is a window over the arrangement's one notes[] array, never a copy (that would fork note.beat-as-truth); an audio region is a non-destructive pointer into immutable media.
• src/track-session.js — threads regions[] through _trackSessionNormalizePure (attached only when non-default), bumps editor_track_session to v3, teaches _trackSessionIsDefaultPure about regions.
• routes.py — _coerce_track_regions mirrors the frontend so authored regions survive the save→build round-trip (tracks are rebuilt field-by-field, so an unknown field would otherwise be stripped); version 2→3.

Guarantees (both tested)

• Migration is invisible — a v2 pack (no regions) resolves to exactly one full-span region per track, identical to today.
• Byte-identical — a lone default region writes no regions key, so untouched packs don't churn on save.
• v3 is purely additive — v2 trees need no migration; the bump gates nothing.

Tests

tests/track_regions.test.mjs (11) + tests/test_track_regions.py (7), all fail on main. Full suite green: JS 296/0 · pytest 365/0 · lint 0 errors.

What's next

PR 2 renders the region strip + selection; PR 3 is the import-into-existing-project driver (place/move/delete); PR 4 adds non-destructive audio-region playback + trim.

🤖 Generated with Claude Code

https://claude.ai/code/session_017xGPjDBF8NTwTK7VQvizix

Summary by CodeRabbit

• New Features

  • Added support for optional regions on audio and transcription tracks.
  • Regions can define timeline positions, labels, mute state, and audio trimming.
  • Existing content continues to resolve to a single full-track region when no regions are specified.

• Bug Fixes

  • Improved validation, ordering, deduplication, and handling of invalid region data.
  • Preserved compact, byte-identical saves when only default regions are present.

• Tests

  • Added comprehensive coverage for region normalization, persistence, migration, and timeline boundaries.

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 206e9df6-c408-4075-bb7c-f44cc22d6554

📥 Commits

Reviewing files that changed from the base of the PR and between 7b7e716 and 86854bb.

📒 Files selected for processing (3)

• routes.py
• src/region.js
• tests/track_regions.test.mjs

📝 Walkthrough

Walkthrough

Adds a region data model for tracks, normalizes and persists authored regions[] on audio and transcription tracks, bumps editor_track_session to v3, omits implicit default regions, and adds backend and JavaScript coverage.

Changes

Track regions

Layer / File(s)	Summary
Region model and normalization src/region.js	Defines default-region resolution, validation, trimming and label normalization, deduplication, sorting, default detection, and beat containment.
Track-session persistence routes.py, src/track-session.js	Sanitizes and persists non-default regions for audio and transcription tracks, omits default regions, preserves default-tree detection, and emits schema version 3.
Region and persistence validation tests/test_track_regions.py, tests/track_regions.test.mjs, CHANGELOG.md	Adds coverage for normalization, migration, persistence, YAML round trips, idempotency, and documents the v3 groundwork.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant TrackSession as track-session.js
  participant RegionModel as region.js
  participant Routes as routes.py
  TrackSession->>RegionModel: normalize track regions
  RegionModel-->>TrackSession: normalized non-default regions
  TrackSession->>Routes: persist normalized track session
  Routes->>Routes: sanitize regions and stamp version 3
  Routes-->>TrackSession: session payload

Loading

Possibly related PRs

• got-feedBack/feedBack-plugin-editor#285: Establishes the track-session persistence and coercion layer extended here.
• got-feedBack/feedBack-plugin-editor#289: Provides adjacent v2 track-session persistence wiring.
• got-feedBack/feedBack-plugin-editor#292: Modifies the same session normalization path extended with v3 regions.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the core change: track regions data model and migration, with no UI work yet.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch track-regions-p1

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

src/region.js (1)

34-37: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Allow 0 to evaluate as valid rather than relying on the fallback.

Both _nonNegNumPure and _region_num_pos are designed to ensure non-negative numbers, but their strict > 0 checks reject valid zero inputs and rely on their default fallbacks (which happen to be zero) to produce the correct result. Using >= 0 avoids this logic quirk and prevents bugs if a non-zero fallback is ever used.

• src/region.js#L34-L37: change the condition in _nonNegNumPure to Number.isFinite(n) && n >= 0.
• routes.py#L556-L562: change the condition in _region_num_pos to math.isfinite(n) and n >= 0.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/region.js` around lines 34 - 37, Update _nonNegNumPure in
src/region.js:34-37 and _region_num_pos in routes.py:556-562 to accept finite
zero values by changing their positivity checks from strictly greater than zero
to greater than or equal to zero, while preserving fallback behavior for invalid
numbers.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/region.js`:
- Around line 31-33: Update _regionIdPure to trim the string before validating
its length, and check the trimmed value against the 160-character limit.
Preserve the existing empty-string result for non-string, blank, or over-limit
values.

---

Nitpick comments:
In `@src/region.js`:
- Around line 34-37: Update _nonNegNumPure in src/region.js:34-37 and
_region_num_pos in routes.py:556-562 to accept finite zero values by changing
their positivity checks from strictly greater than zero to greater than or equal
to zero, while preserving fallback behavior for invalid numbers.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8e36b207-b20c-4151-9ab7-55b14d9e90cd

📥 Commits

Reviewing files that changed from the base of the PR and between b0bf875 and 7b7e716.

📒 Files selected for processing (6)

• CHANGELOG.md
• routes.py
• src/region.js
• src/track-session.js
• tests/test_track_regions.py
• tests/track_regions.test.mjs