Feat/story deeplinks

[theshantanujoshi]

PR Description: Implement Story Deeplinks & Share-to-Clipboard

This PR implements deep-linking support for cinematic stories (Issue #29), enabling users to share specific moments and maintain story state across browser sessions.

Changes

1. URL State Synchronization

• Bidirectional Sync: The application now reads story, beat, and paused parameters from the URL on mount.
• State Reflection: As the story progresses, the address bar is updated via window.history.replaceState to allow for easy bookmarking and link sharing without page reloads.
• Cleanup: Parameters are automatically removed from the URL when a story is ended.

2. Share Interface

• One-Click Share: Integrated a new "Share" button (Network icon) into the StoryControls component.
• Clipboard Integration: Copies the current state-synchronized URL to the clipboard.
• Visual Feedback: Implemented a 2-second "Copied" transition (Check icon) with motion for polished user feedback.

3. Architecture

• Store Extension: Updated the global store to support starting a story at a specific beat index.
• Component Integrity: Centralized initialization logic in AppShell to ensure robust client-side state recovery.
• Motion Standards: All transitions and feedback animations respect prefers-reduced-motion.

Verification Checklist

• npm run typecheck passes.
• Navigating to ?story=rise-of-vader&beat=2 starts the story at the 3rd beat.
• "Share" button correctly copies the deep-link with the current beat index.
• URL parameters are cleared upon clicking the "X" (End Story) button.
• Invalid story IDs in the URL are gracefully ignored.

Related Issues

Closes #29

[safedep]

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[adhit-r]

Holding this before merge. npm run typecheck passes, but git diff --check fails in components/cinematic/StoryMode.tsx and components/game/MemoryPalace.tsx.

There is also a deeplink parsing bug: parseInt(beatStr, 10) can produce NaN for URLs like ?story=rise-of-vader&beat=abc, and that value is passed into playStory. StoryMode then writes beat=NaN back to the URL and the timer keeps advancing NaN. Please validate/clamp the beat parameter before storing it.