941a37494b
CSS: reduce backdrop-filter to modals only, add contain/content-visibility for inactive tabs, optimize transitions to background-color, pre-compute color-mix results, add container queries, split themes to lazy-loaded file. JS: cache DOM refs in render path, add field-level diffing for SSE updates, replace innerHTML with replaceChildren() in hot paths, add WebGL colour cache invalidation on theme switch. HTML: add defer to scripts, lazy-load plugin scripts on tab activation, SVG sprite sheet for tab icons, template elements for deferred tab content, improve aria-live/keyboard nav/colour contrast accessibility. Server: upgrade Cache-Control to immutable, add Brotli compression alongside gzip with Accept-Encoding negotiation. Implements all items from docs/frontend_improvements.md except app.js ES module split (P1, requires major refactor) and Web Worker migration (P3). https://claude.ai/code/session_015rQNMGvusj5jY66MPUgYqt Signed-off-by: Claude <noreply@anthropic.com>