add automated test coverage for sequencer editing workflow to prevent regressions

[dvschultz]

Summary

Add a minimal automated test (UI or model-level) that exercises key sequencer edit operations and verifies persistence to catch regressions before release.

Source

• File: GMT20260505-000858_Recording.m4a
• Path: /Volumes/Lexar/2026 DADA ZOOM/Week 4/GMT20260505-000858_Recording.m4a
• Transcript time: 00:02:25 - 00:02:37

Evidence

Sequencer editing recently broke and was fixed; needs regression coverage (GMT20260505-000858_Recording.m4a 145–157)

Acceptance Criteria

• Test creates/loads a project with multiple clips and opens the sequencer (or sequencer model)
• Test performs at least one edit operation (add clip, reorder, trim, save) and asserts persisted state
• Test runs reliably in headless mode or via a documented local test runner

Implementation Notes

Use pytest-qt or test sequencer data model + serialization if full UI automation is too heavy.

Extraction confidence: 0.64