fix(web): worker detail loads fast — stats from summary + lightweight flow + SWR tab cache

[federicodeponte]

Problem

The authed worker-detail page (floom.dev/app → /workers?sel=<id>, the split-pane operators live in) is sluggish:

• Overview stat cards (Last run / Runs / Success) sit on "Loading" for seconds.
• The Flow section shows a persistent grey skeleton.
• Tab switches (Overview/Runs/Setup/Source/…) are slow.

Root cause

OverviewTab blocked its stat cards and the flow on the full GET /workers/{id} payload, which the backend documents as ~6-8s warm / tens of seconds cold on Cloud (recent runs + latest-run output + ~3s stats batch + recipe + secret/connection availability + on-disk bundle materialize). The 3 stats need none of that — they come from recent_stats/last_run already on the list summary.

Separately, #2186 shrank the detail cache freshness to 250ms, which effectively disabled the "cached so tab switches don't refetch" behavior and re-fired the heavy fetch on nearly every tab click.

Fix

• Stats render instantly from the list summary and upgrade to fresh detail values when it arrives (stale-while-revalidate). No more "Loading" text sitting for seconds.
• Overview flow uses the existing lightweight ?shape=run fetch (config only) → resolves in <1s instead of blocking on the heavy assembly. The full detail loads in the background to warm the file-backed tabs (Source/Setup/Versions/Tools/Library) so they're instant on first click.
• Detail cache → stale-while-revalidate + 30s fresh window: a cached detail is served immediately on tab switches (never re-blanks to a spinner) and revalidated in the background. Cross-workspace safety (fix(web): prevent stale dashboard renders #2186's concern) is preserved by the workspace-scoped cache key, not a tiny freshness window.
• Home stat-card sparkline tooltip: dropped the overflow-hidden wrapper that was clipping the hover tooltip into card content.

Expected speedup

Opening a worker: stat cards resolve in <100ms (were 6-8s), flow in <1s (was 6-8s). Tab switches: instant from cache after first load (were a fresh 6-8s refetch each).

Verification

• vitest: updated workers-overview-flow-schedule + 9 other worker-detail DOM suites (40 tests) green; stale-closure timeout regression test green.
• tsc --noEmit: 0 errors in changed source (37 pre-existing test-file errors unchanged).
• eslint, lint:detail-tabs, lint:borders, lint:tokens: clean.
• Live floom.dev/app verification pending Fede's authed session (2FA); fix verified by code path + build + tests.

Notes

workers-overview-flow-schedule.dom.test.tsx previously asserted the stat summary must show "Loading" and hide the summary's run count until the heavy detail loaded — that encoded the exact slow behavior being fixed, so it now asserts stats render from the summary immediately while the flow shows its skeleton.

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