perf(quiescence): ambient decorative animations never pause — adopt an idle-quiescence rule

[jdmanring]

Principle

A quiescent Odysseus should generate ~zero frames. Today several ambient decorative animations run perpetually to look 'alive', each keeping the compositor awake and preventing idle quiescence. Cheap on a healthy GPU, but: (a) real battery/power cost on laptops/tablets, (b) catastrophic when rendering falls back to software (see the llvmpipe incident — a handful of these summed into a 12-core freeze), (c) against our 'never waste CPU/GPU frivolously' rule.

Known instances (the class, not just one bug)

• Research orbit ring — full-area conic-gradient + mask repainted every frame while the panel is open, even idle (perf(research): orbit ring repaints the whole pane every frame, forever (perpetual conic-gradient + mask raster) #115).
• Notes quick-add — notes-quick-pulse (2.8s infinite opacity pulse) and notes-quick-caret (1s steps(2) infinite fake caret), static/style.css:32174/32222; pause only on hover/focus-within, otherwise run forever while visible.
• Prior fixes in this family: spinner orphan loop (Whirlpool spinner rAF loop never terminates when element is never appended (or is hidden): perpetual CPU + canvas churn #107), Brain/Notes panel animations (Brain/Notes panel CSS animations generate continuous raster tiles; compositor-promote and make memory sweep hover-triggered #108).
• Structural cousins from docs/fork/perf-audit-2026-06.md: C3 (infinite CSS animations off-screen), D1 (modalManager 1s scan), D2 (always-on polls).

The rule to adopt

Ambient/decorative animations must pause when not needed: window blurred / page hidden (visibilitychange), panel unfocused or off-screen, or prefers-reduced-motion. Prefer compositor-only properties; never animate paint-inducing properties over large areas perpetually. New animations should default to quiescent-when-idle.

Tracking

This issue owns the class. Instance fixes: #115 (orbit), notes quick-add (in progress). Pairs with #116 (graceful degradation = the safety net; this = the prevention).

[jdmanring]

Instances landed (both cherry-picked to develop, staged for upstream):

• Notes quick-add pulse/caret — fix/notes-quick-idle-quiescence. Added the reusable primitive html.app-blurred (toggled in ui.js on blur/visibilitychange); CSS pauses the animations under it.
• Research orbit ring (perf(research): orbit ring repaints the whole pane every frame, forever (perpetual conic-gradient + mask raster) #115) — fix/research-orbit-quiescence. Runs only during active jobs; quiesces on hidden/reduced-motion; ~30fps throttle.

The primitive (html.app-blurred) is in place for the remaining instances (audit C3 subset, etc.).