feat: add AI Design Session Replay & Prompt Evolution Timeline System

[surjeetkumar8006]

Closes #1138

✨ Overview

Currently, Reframe focuses on client-side resizing and video adjustments, but there was no structured way to visualize, track, or replay layout edits and prompt iterations over time. This PR introduces a client-side AI Design Session Replay & Prompt Evolution Timeline System that allows users to write natural language styling prompts, scrub/replay their edit history step-by-step, compare changes side-by-side (diffs), bookmark milestone states, and recover layout sessions automatically.

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🎨 Proposed Features

1. 🎬 Design Replay Timeline:
   • Visual timeline displaying chronological manual and AI-generated recipe states.
   • Replay controls (Play, Pause, Step Back, Step Forward, Scrubbing Slider) that transition the design settings in real-time.
2. ✍️ Prompt Evolution Tracking:
   • Client-side AI Compiler (src/lib/sessionHistory.ts) that interprets compound natural language prompts (e.g., "make it vertical, increase contrast and add text 'Vlog'") and updates settings.
   • Logs what operations were applied and builds a prompt evolution chain.
3. 🧩 Visual Parameter Diff Comparison:
   • Interactive dropdown selectors to compare any two session states.
   • Color-coded badges indicating exactly what parameter was added, removed, or modified.
4. 📊 Workflow Analytics:
   • Statistics dashboard summarizing editing category distribution, session depth, and prompt effectiveness rating.
5. 🏆 Milestone Snapshots:
   • Bookmark design checkpoints as Milestones (e.g., "Cinematic Version", "Instagram Reel draft").
6. 🔄 Intelligent Recovery & Auto-Rollback:
   • Restores the design timeline from localStorage on page reload.
   • Automatically prompts and applies rollbacks to stable milestones or previous states on video export errors.

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🛠️ Technical Details

• Files Created:
  • src/lib/sessionHistory.ts: State representation, localStorage handlers, recipe diff calculations, and client-side AI compiler.
  • src/components/AICopilotTimeline.tsx: Premium dashboard component with tabs for Copilot prompts, Evolution Timeline/Replay, Parameter Diff, and Stats.
  • src/components/__tests__/sessionHistory.test.ts: 7 detailed unit tests verifying compiler behavior and diff logic.
• Files Modified:
  • src/components/VideoEditor.tsx: Intercepts manual edits with a 1.2s debounce to record checkpoints, integrates the timeline switch tab, and handles errors with rollbacks.

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🧪 Testing & Verification

• Unit Tests: Executed npm run test using Vitest. All 84 tests in the project passed successfully.
• Production Build: Verified clean static build using npm run build with zero TypeScript or ESLint errors.

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[github-actions]

👋 Thanks for your PR, @surjeetkumar8006!

Welcome to Reframe — a browser-based video editor built for everyone 🎬

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• Linked the issue this PR closes (e.g. Closes #123)
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• 📖 CONTRIBUTING.md
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Happy coding! 🎉

[github-actions]

✅ PR Format Check Passed — @surjeetkumar8006

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[surjeetkumar8006]

Hi @maintainers
This is a fully implemented advanced feature with replay timeline, prompt evolution tracking, visual diff comparison, analytics, milestones, and recovery system.

✅ Tests passing
✅ Build successful
✅ Integrated cleanly into existing workflow

Would appreciate a review and merge when possible. Thank you 🚀