fix(interactions): give factories a live view of the animation

[Gamote]

What

useInteractionsRunner handed every factory the current animation through a getter on the context. The animation object a hook returns is rebuilt on every render, so a factory that kept what it was handed, const { lottie } = context, the natural thing to write, kept that render's values: root stayed null when the element mounted after attach, which on a prerendered page is always. The two shipped factories read the context on every use and were unaffected; the docs' custom-factory example was not, and never armed on a direct load.

The context now carries one live view per animation: an object whose members are getters onto the current instance, built from the instance's own keys (the same shape React Hook Form uses for its proxied form state), cached per animation for the runner's life. Keeping or destructuring it is safe; a value pulled out of it is a copy of that moment, as any value is. No public type changes. The custom-factory example returns to the destructuring form, and the contract's JSDoc and the "Writing your own" page say the view is live.

Verified

• Two new tests, red-first on the old runner: a copy taken at attach sees the root arrive, the state move and its commands reach the animation, and exposes every member of the instance; the view is one stable object across reads and across a re-arm. The six identity assertions on context.lottie now prove "this context drives that animation" through subscribe, one function per animation for its life.
• pnpm check green: 480 tests, coverage 100 / 97.43 / 100 / 100, budgets unchanged, 34 pages rendered.
• Real browser: the built site's destructuring example registers its listener and plays on a direct load of "Writing your own"; the packed build in a Next.js 16 Turbopack app, a prerendered page with a destructuring factory, direct-loaded: plays while pressed and pauses on release, where the previous build stayed on frame 0.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.91%. Comparing base (aace264) to head (0589b7d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #136   +/-   ##
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  Coverage   99.91%   99.91%           
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  Files          47       47           
  Lines        1223     1232    +9     
  Branches      361      362    +1     
=======================================
+ Hits         1222     1231    +9     
  Misses          1        1           

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