Build meter: settle before drawing a new scene, choreographed changes, outcome faces

[briansrls]

Stacked on #13500. Its own commits are the last two; rebase onto main once #13500 lands.

What changes

• No jitter. The meter takes its facts (accessible name, digest, ×N badge, link) on every revision at once, but draws a new scene only after it has held for 6 s. A revision back to the drawn scene cancels it. Stopped and published are drawn as soon as they're seen.
• Changes are animated, never cut. A change plays choreography rows over the leaving and arriving server-rendered stills inside a canvas, over 800 ms: z's, marks and the old gold rule fade; the worker walks in two-unit steps with a bob (getting up first if it was sitting); the gold rule wipes in; the stop cap draws up; the arriving pose takes over and its z's drift in. A paused (stale) worker crossfades instead. Under reduced motion the dwell still applies and the drawing is replaced without animation.
• The page hands renderings to the meter. The workflow observation keeps its revision race guard and dispatches an accepted rendering to the meter by event, instead of swapping innerHTML.
• Poses by outcome (owner rulings 2026-10-06). Waiting for a serving seat naps on the floor; the waiting room is removed. A published worker is content: eyes closed in arcs, a small smile, antenna lit green. A failed one is sad: drooped lids, a frown, antenna lit red. A spent step budget stays deadpan. The antenna ball is six units across with cut corners, so it reads as a ball rather than a cross.
• Specimen. The build meter's sections gain "changes of scene": one attempt rendered in every scene, with controls that hand each drawing to a live meter, and a flap control that switches faster than the dwell.
• Adds ClipPath and GridArea to the typed CSS properties and a SlotMeterSuccess palette slot.

Evidence

• site_build_meter_witness_test: 42/42 pass; site_element_witness_test: 69/69 pass. The most expensive claim takes 59,340 eval steps, under the new-witness ceiling.
• New claims cover: each drawing states its scene, settle rule, stance and worker place; the cue table finishes under a second and removes every leaving part; cues run only while the canvas carries the changing class, and reduced motion stills them; the client holds a new scene for the dwell; the poller dispatches to the meter rather than swapping it in; the face follows the outcome.
• Checked in a browser with Playwright against real server-rendered stills, which is an ad hoc check and not a CI test:
  • a scene flapping six times at 2 s intervals was never drawn;
  • a scene that held was drawn at the 6 s mark;
  • stopped and published were drawn at once;
  • under reduced motion the dwell held and the drawing changed without animation;
  • frames were captured across 0–800 ms for every pose pair, in both themes.

🤖 Generated with Claude Code

[briansrls]

Folded into #13500 (its branch now carries these two commits, fb2a813) so the overhaul and the meter transitions land in one queue cycle. Closing this one.