Optimize animated trail rendering

[spencerc99]

Summary

• Reduces per-frame work in the animated trails hot path by caching finished trail frames, avoiding redundant SVG/path mutations, and reusing frame scratch collections.
• Preserves the newer trail overlap behavior by layering active path groups so active heads paint over earlier or finished trail bodies.
• Memoizes movement canvas trail settings and keeps the trail visual style comparator current.

Validation

• git diff --check
• bun --bun run vitest run website/shared/utils/__tests__/trailAnimation.test.ts website/shared/styles/__tests__/trailRenderers.test.ts
• bun --bun run vitest run in extension (117 tests passing)
• bun --bun run build in extension/website

Notes

The website build still emits pre-existing Sass deprecation warnings. The extension tests still emit the existing participant fallback stderr logs.

[pkg-pr-new]

Open in StackBlitz

bun add https://pkg.pr.new/@playhtml/common@115

bun add https://pkg.pr.new/playhtml@115

bun add https://pkg.pr.new/@playhtml/react@115

commit: ff12a30

[cloudflare-workers-and-pages]

Deploying we-were-online-website with    Cloudflare Pages

Latest commit:	ff12a30
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Preview URL:	https://537d13f1.we-were-online-website.pages.dev
Branch Preview URL:	https://codex-perf-animated-trails.we-were-online-website.pages.dev

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