refactor(editor): extract smoke export progress sampler

[meiiie]

Description

Extracts the smoke-export progress sampling logic out of VideoEditor.tsx into a small smokeExportProgress module with focused unit coverage.

Motivation

handleExport is one of the remaining orchestration-heavy areas in VideoEditor.tsx. The smoke-export progress sampler is a low-risk extraction target because it is local, deterministic, and does not touch exporter construction, save/finalize behavior, native export, or rendering.

Type of Change

• Bug fix
• Refactor
• Feature
• Documentation

Changes Made

• Added createSmokeExportProgressSampler for smoke export report sampling.
• Added tests for disabled/no-start behavior, first sample, interval sampling, phase changes, and final-frame sampling.
• Replaced the inline sampler state inside handleExport with the extracted module.

Scope

This PR intentionally does not refactor exporter config construction, save handling, native export, or runtime rendering paths.

Testing Guide

1. Run the targeted Vitest tests.
2. Run TypeScript typecheck.
3. Run scoped Biome checks.
4. Optionally run smoke export and confirm .report.json still includes progress samples.

Verification

• npm test -- src/components/video-editor/smokeExportProgress.test.ts src/components/video-editor/smokeExportConfig.test.ts
• npx tsc --noEmit --pretty false
• npx biome check src/components/video-editor/smokeExportProgress.ts src/components/video-editor/smokeExportProgress.test.ts
• npx biome lint src/components/video-editor/VideoEditor.tsx
• git diff --check

Summary by CodeRabbit

• Refactor

  • Improved video export progress tracking with refined sampling logic.

• Tests

  • Added comprehensive test suite for export progress functionality.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: ab2a2e2b-7264-4402-93a6-a8259a6e6e66

📥 Commits

Reviewing files that changed from the base of the PR and between 7b3eaaa and f4a68ca.

📒 Files selected for processing (3)

• src/components/video-editor/VideoEditor.tsx
• src/components/video-editor/smokeExportProgress.test.ts
• src/components/video-editor/smokeExportProgress.ts

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📝 Walkthrough

Walkthrough

Introduces a new smoke export progress sampling utility that conditionally records export state transitions and collects timestamped samples based on phase changes, elapsed time intervals, and completion. VideoEditor integrates the sampler to replace inline progress tracking during MP4 export. Tests validate all sampling conditions.

Changes

Smoke Export Progress Sampling

Layer / File(s)	Summary
Smoke export progress sampler implementation src/components/video-editor/smokeExportProgress.ts	SmokeExportProgressSample type and createSmokeExportProgressSampler factory record timestamped export state based on enabled flag, phase changes, configurable sampling interval, and completion state.
Sampler tests and progress helpers src/components/video-editor/smokeExportProgress.test.ts	Test helper factory constructs ExportProgress objects with defaults. Test suite validates disabled mode, unknown start time, first-update defaults, same-phase skipping within interval, phase-change sampling, and final-frame inclusion.
VideoEditor integration src/components/video-editor/VideoEditor.tsx	Imports sampler factory and instantiates it during MP4 export, replacing inline sampling state and callback with the sampler's record method and samples array.

Sequence Diagram

sequenceDiagram
  participant VideoEditor
  participant Sampler as Smoke Sampler
  participant Samples as Sample Array
  
  VideoEditor->>Sampler: createSmokeExportProgressSampler({enabled, startedAtMs})
  activate Sampler
  Sampler->>Samples: initialize empty array
  deactivate Sampler
  
  loop on each export progress update
    VideoEditor->>Sampler: record(exportProgress)
    activate Sampler
    alt sampling triggered
      note over Sampler: phase changed OR<br/>interval elapsed OR<br/>isLastFrame
      Sampler->>Samples: append timestamped sample
    end
    Sampler-->>VideoEditor: return { record, samples }
    deactivate Sampler
  end
  
  VideoEditor->>VideoEditor: use samples for telemetry

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

Checked

Poem

🐰 A sampler hops through export time,
Collecting progress, phase by phase,
Each interval marks a milestone fine,
While VideoEditor keeps steady pace,
Tests ensure no sample falls behind! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main refactoring: extracting smoke export progress sampler logic into a dedicated module.
Description check	✅ Passed	The description covers all essential template sections: purpose, motivation, type of change, related changes, testing guide, and verification steps with specific commands.
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.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/editor-export-progress-sampling

Warning

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🔧 ESLint

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