perf(research): orbit ring repaints the whole pane every frame, forever (perpetual conic-gradient + mask raster)

[jdmanring]

Problem

The Research pane's animated accent ring is a perpetual per-frame paint producer.

static/js/research/panel.js:_ensureOrbit() runs a requestAnimationFrame loop that rewrites the --research-orbit-angle CSS variable every frame while the panel is open — by design even when idle with no research job running (ambient mode, _orbitSpeedDegPerSec = running > 0 ? 60 : 22). The loop only stops when the pane is removed.

That variable feeds static/style.css .research-pane::after:

.research-pane::after {
  position: absolute; inset: 0;                 /* full pane area */
  background: conic-gradient(from var(--research-orbit-angle), …);
  mask: …; mask-composite: exclude;             /* dual-mask to a 2px ring */
}

Every frame the browser recomputes a conic-gradient over the entire pane box and re-applies an exclude mask-composite, then re-rasterizes — 60 fps, forever. This is the worst-case 'paint, not compositor' pattern (large area + mask), and it is invisible work when idle (no job, user not looking).

Impact

Discovered via CDP (tooling/mem-probe.py raf flagged _ensureOrbit <- _syncResearchRail). On hardware GPU it's a steady background cost; under software rendering (llvmpipe) it is catastrophic. Same family as the spinner (#107) and brain-panel (#108) perpetual-animation fixes, but worse (full-area + mask).

Proposed fix

• Freeze the orbit when no job is running (the ambient idle spin is pure decoration burning frames) — leave a static ring; only drive the rAF while running > 0. Eliminates the idle case entirely.
• When it does run, prefer a compositor approach (static gradient + transform: rotate()) or throttle below 60 fps. Note: a traveling arc around a rounded-rect can't be fully compositor-free, so freezing-when-idle is the high-value win.
• Honor prefers-reduced-motion (already partially done — the ::after has a reduce rule, but the JS rAF ignores it; gate the JS too).

Evidence: this session's CPU investigation; static/js/research/panel.js:160-183, static/style.css:35927.

[jdmanring]

Implemented on fix/research-orbit-quiescence (cherry-picked to develop). The orbit rAF now runs only while a research job is active (_orbitActive = running > 0), pauses on document.hidden / prefers-reduced-motion, throttles the repaint to ~30 fps, and re-evaluates on visibilitychange. When idle the ring holds a static angle (still visible, zero cost). Kept the conic-gradient visual; eliminated the perpetual idle repaint. 5 static guards in tests/test_research_orbit_quiescence.py. Staged for upstream.

[jdmanring]

Resolution changed: REMOVED, not optimized. Measured the compositor version's GPU cost via CDP LayerTree — the rotating-gradient layer was a 1633×5155 texture ≈ 32 MB (the width/height:250% oversize scaled by a hi-res pane). Odysseus runs local models, so that VRAM is the model's context window; spending ~20-32 MB on a decorative border is the wrong trade on any device and can OOM a marginal model. Removed the orbit entirely (DOM + CSS + class toggle); job activity is already shown by the rail pulse / running dots / round counter. Tests now guard against re-adding a will-change layer in the research pane.