feat(mascot): rework grok's hover and click motion

[RealZST]

Reworks the Grok mascot's motion, plus two bits of cleanup found on the way.

Motion

The mark is ambiguous — it reads as a star with something going round it, and equally as the spinning top it resembles. The two states each take one reading, and share no motion on purpose: a small preview of the spin on hover would spend the click in advance.

Hover. The star holds still and a planet crosses it on a drawn elliptical trajectory whose dashes flow along the path. The planet is a grey four-point flare inside a halo, scaled and faded along the orbit so the near point is large and bright and the far one small and dim. Grey rather than the mark's own colour, so it reads as a second, lesser body rather than a chip off the star.

Drawing the trajectory is what makes the orbit legible. Everything in the mascot is one currentColor, so the planet is swallowed wherever it crosses the mark and there is no drawing it in front. Without the path that reads as a blink; with it the dashes carry on where the planet went, so it reads as passing behind.

The star has to hold still for a second reason: the click stands the mark up from 0deg, so any idle rotation would be mid-turn when a click began and the mark would snap back to 0 to start.

Click. It crouches, hops, and is stood upright -45deg into the ascent, then turns about the vertical axis as it lands and runs down to a stop before unwinding back to brand angle.

-45deg is measured, not chosen: the line through the two spikes sits at exactly that angle, so it stands the mark on its tail with the ring square to the vertical. +45deg lays it on its side instead, and +135deg is pixel-identical to -45deg because the glyph maps onto itself under a half turn.

The three tracks sit on three nested elements, one job per layer:

layer	hover	click
wrapper	—	the hop, and the squash on touchdown
<svg>	—	the spin
<path>	—	stood upright, then unwound
<circle>/<ellipse>	the orbit	cut

The nesting is load-bearing rather than tidiness. A child's transform composes before its parent's, so putting the upright rotation on the path and the spin on the svg spins an upright mark; either one on an ancestor of the other, or both on one element in the other order, tilts the axis it spins about by 45 degrees instead.

CLICK_DURATIONS.grok goes from 900ms to 2100ms. The old value pulled is-clicked while the mark was still held at 45deg, cutting the unwind.

Everything the orbit adds is transparent at rest, so the extension tables, the marketplace and the kit drawer are unchanged — only agent-card.tsx passes animated, and it already leaves grok on overflow-visible for the orbit to overhang.

Cleanup

Screenshots. The three PNGs under media/pr-grok-build/ only ever illustrated #125. Nothing in the repo references them, and that PR's body points at raw.githubusercontent.com on the contributor's fork rather than at this repository, so removing them here leaves the thread's images intact.

Dead cursor CSS. .shadow-el has no element behind it — cursor-mascot.tsx renders only .rocker and .icon-svg. Four rules and two keyframe blocks have been styling nothing since the shadow was dropped from the markup.

Biome. npm run lint was reporting on three files this branch does not otherwise touch. CI runs test and build but not lint, which is why they went unnoticed. Last commit, separable.

Checks

npm test 307 passing, npm run build clean, npm run lint now clean.