Each in-flight (or stuck) embedding job gets a colored health pill,
relative-activity timestamp, and chunk counter so users can tell at a
glance whether ingestion is making progress.
## Health states
- **🟢 Active** — last batch < 2 min ago
- **🟡 Slow** — last batch 2-5 min ago (CPU-paced multi-batch ingestion
lives here naturally; not always a problem)
- **🔴 Stalled** — last batch > 5 min ago (likely real problem)
- **⚪ Waiting** — queued, no batch started yet
- **🔴 Failed** — job recorded failed status
## What lands
- New backend util `kb_job_health.ts` with pure `computeJobHealth(input)`
decision function. Time-based thresholds (2 min / 5 min) inlined as
constants. 9 unit tests pin the boundaries.
- `EmbedJobWithProgress` gains `lastBatchAt`, `startedAt`, `chunks` —
already set by `EmbedFileJob.handle` on every batch transition, just
not previously surfaced through `listActiveJobs`.
- Frontend `kb_job_health_display.ts` maps each status to a Tailwind
dot color, label, and aria-label so backend and UI stay in sync.
- `ActiveEmbedJobs.tsx` renders the pill, "last activity Xs ago", and
chunk counter above each progress bar. Adds a manual Refresh button
and "Last updated Xs ago" line — the existing 2s/30s auto-poll
cadence in `useEmbedJobs` is left intact.
- Live tick at 5s keeps the relative timestamps current without
re-fetching from the API.
## Not in scope
- Per-card Cancel / Retry / Un-index — separate Phase 2 PR
- Conditional warnings A/B/C — separate Phase 2 PR
- Computing throughput rate (chunks/min) — needs ratio registry consumer
(Phase 2 follow-up); for now the pill answers the "is it stuck?"
question directly without a rate estimate.
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