fix(web): pulse running V2 worker icons

[saphid]

What Changed

Running V2 worker icons now breathe in Lineage and their timeline links. Waiting, pending and finished workers stay still, as do parent and fork relationship icons.

Why

The static blue badge made a running worker look the same as one waiting for input. Reuse the existing two-second stepped opacity pulse and shared visibility observer. Motion stops off-screen or in hidden tabs, and reduced-motion preferences disable it.

The change is in the web UI shared with desktop. Provider adapters, wire contracts and mobile are unchanged.

Verification

• 11 tests passed across ThreadRelationshipsControl.test.tsx, ThreadRelationshipsControl.agents.test.tsx and visibleAnimation.test.ts with vp test run.
• Targeted vp lint and vp fmt --check passed for all three changed files.
• vp run --filter @t3tools/web typecheck passed.
• Integrated Chrome check: base had zero animations; candidate animated exactly the three running workers. Waiting, pending and completed workers had no animation. Emulated reduced motion disabled all three pulses.
• Independent Fable 5.1 standards and requirement reviews completed. A follow-up review confirmed the parent/fork exclusion fix and found no remaining concrete defect.

UI Changes

Disposable synthetic lineage data, dark theme, 1200 × 900 CSS-pixel viewport. Base a74e16065bf, candidate 75081e6bd6f. These approximately six-second GIFs come from actual Chrome recordings with capture timestamps and no speed change. The baseline scene is static. The recordings predate a history-only rebase onto 640dd532493; the three changed components, visibility helper and stylesheet are byte-identical at the current head d814253c650. Browser verification covers the shared web UI; no native desktop or mobile run was performed.

The screenshots look identical because the candidate was captured during the pulse's full-opacity phase. The GIFs and videos show the motion.

Before: running workers have static icons.

Before recording · Before screenshot

After: only the three running worker icons breathe.

After recording · After screenshot

Port note (2026-09-24)

Ported onto upstream OV2 t3code/codex-turn-mapping at 692ad0a8fd as one commit (3ffc15958d). Upstream now renders timeline subagent links with SubagentAvatar instead of ThreadRelationshipIcon, so the same pulse (stepped opacity, visibility-gated, motion-safe) is applied to SubagentAvatar only from the timeline link; overlapped avatar stacks stay still. The evidence below was captured on the earlier rehearsal base, before this port, and the timeline avatar now looks different upstream.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Implemented by GPT-6 Astra in Codex. Reviewed by Fable 5.1 through T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at 4b0eb3e

Macroscope's review found this PR approvable — The PR makes a focused web UI adjustment that adds visibility- and reduced-motion-aware pulsing only to explicitly selected running worker icons. It does not alter data contracts, workflows, product configuration defaults, or static-analysis settings.

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Dismissing prior approval to re-evaluate 6f299d2

[macroscopeapp]

Macroscope has since reviewed this pull request. An earlier review was skipped by a cost limit; a review has now completed, so that notice no longer applies.

Dismissing prior approval to re-evaluate 4b0eb3e

[juliusmarminge]

Superseded by #14412 (steady status labels instead of pulsing icons).