Read docs/PROMPT_stability_panel.md

# Prompt — "Stability across seeds" panel in the Lab (HNSC/HPV)

Add a multi-seed stability panel to the Lab that reruns the HPV search across
several seeds and shows (a) how tightly the result holds and (b) which genes
recur across independent searches. **Frontend-only** — reuse the existing run,
transfer, reveal, and full-rank endpoints. No engine / API / airgap change.
`tsc` after.

Gated to `dataset === "hnsc" && target === "hpv"` (hidden otherwise). Everything
this needs already exists on the wire; do not add a backend endpoint.

---

## What it does
For each seed in a list (default `[1, 3, 7, 11, 13, 17, 23, 29]`), fire a normal
HPV run with that seed, wait for it to finish, then pull its held-out result and
its independent-cohort transfer. Aggregate across seeds into one panel.

## Data flow (all existing endpoints)
- Fire a run: `postRun({ objective_spec: OBJECTIVE_PRESETS.hpv, params: {
  ...params, seed }, engine: "v2", dataset, coherence, diversity, ...ratesDiff })`
  — i.e. the SAME body `launchRun()` builds, only `params.seed` overridden per
  seed. Use the user's current Parameters / coherence / diversity / DSL rates so
  the sweep matches their single-run config.
- Wait for completion **without disturbing the main Live view / Result state**.
  Write a dedicated helper `awaitRunDone(runId): Promise<RunResult>` that opens
  an `EventSource(${API_URL}/runs/${runId}/stream)`, resolves on the `done`
  event (parse `RunResult`), rejects on `error`, and closes the stream — it must
  NOT call `setGenerations` / `setResult` / `setStatus` (those belong to the
  main single-run UI). (Polling `getRunStatus` until done then `getRunResult` is
  an acceptable alternative.)
- Per seed collect: **`winning.holdout_score`** (this is the field the Result
  panel's "Held-out AUROC" card and the verdict display — use it, NOT
  `holdout_auroc`, so the stability dots match the numbers already on screen) and
  `winning.permutation_p` (from the RunResult), then `getRunTransfer(runId)` →
  `auroc`, `p`, `n`, `found_symbols`, `missing_symbols`. If transfer fails (e.g.
  GSE65858 not built), store null for the transfer fields and keep the held-out
  row — never crash the sweep.
- After all seeds: call `getFullRankDiagnostic(dataset, target)` once and build a
  `symbol → set_name` map from `reference_marks` (p16 / cell_cycle) to tag genes.

## Recurrence (the key output)
- A seed's winner symbols come from `postReveal(winning.gene_ids)` — a bounded
  reveal of just that winner's genes (same discipline `/transfer` uses). Source
  it from the winner, not the transfer payload, so recurrence still works even if
  a seed's transfer call failed. (`found_symbols ∪ missing_symbols` from the
  transfer is an equivalent set when transfer succeeds.)
- Tally: for every symbol, count in how many seeds it appears. Sort desc. Tag
  each with its reference set via the map (else "alternate"/"—"). Genes in only
  1 seed collapse into a single "passengers · 1 seed each" row (show the count of
  such genes).

## UI (new `<StabilityPanel>` — match the approved mockup)
Reuse `<SectionCard>`, `<InfoTip>`, `fmtFit`, and the palette tokens so it looks
native. Place it as its own SectionCard in the Result area, after the
independent-cohort validation panel. Gated to hnsc/hpv.

- Header + its own **"Run stability check"** button (independent of the main Run
  button) + a seed-list input (comma or space separated, default the 8 above).
  While sweeping: disable both this button and the main Run button, show
  "Running seed {k} of {N}…", and offer a **Stop** button that sets a cancel
  flag checked between seeds (finish the current seed, then halt).
- **Section 1 — "Does the result hold across seeds?"** Two horizontal dot-strips
  on a 0.5 → 1.0 axis (label "0.5 coin-flip" left, "1.0" right): Held-out AUROC
  (accent-teal dots) and Independent AUROC (amber dots), one dot per completed
  seed, with a light min–max band behind the dots. Caption with the two ranges
  (`min–max`, via `fmtFit`) and a one-line plain read ("tight + high = stable,
  not a lucky seed; the independent cohort costs a little, as expected").
- **Section 2 — "Do the same genes keep coming back?"** Recurrence bars: symbol
  | bar (width = seeds-appeared / N) | "{k} / {N} · {set}". Colour by tag:
  cell_cycle amber, p16 gold, alternate teal, passengers grey. Caption: recurring
  cell-cycle / proliferation genes = real signal; one-off passengers = noise.
- **Section 3 — per-seed table**: seed | held-out AUROC | p | independent AUROC |
  p | genes found/total. Route every number through `fmtFit` ("—" for null).
- Panel `?` (InfoTip): what multi-seed proves — that the result isn't one lucky
  random start (spread), and that the same biology recurs across independent
  searches (recurrence); note each seed is a full run so the sweep takes a while.

## CONSTRAINTS
- Frontend-only. No engine/API/airgap change. Reuse `postRun`, the SSE stream,
  `getRunResult`, `getRunTransfer`, `getFullRankDiagnostic`. The only gene names
  shown are the winner's revealed symbols (already bounded via `/transfer`) and
  the reference marks (bounded known set) — no new reveal surface.
- The sweep must not overwrite the main single-run Result / Live view; it keeps
  its own state (`stabilityRows`, `stabilityStatus`, `stabilityProgress`,
  `stabilityCancel`).
- Runs are sequential (the backend runs one at a time); show progress, allow
  Stop. Graceful nulls if a transfer fails.

## Checkpoint
- On an HNSC/HPV run, a "Stability across seeds" panel appears with a "Run
  stability check" button; clicking it sweeps the seeds, showing live progress.
- When done: two dot-strips (held-out + independent AUROC, one dot per seed with
  the range), a gene-recurrence bar list tagged by reference set, and a per-seed
  table. Hidden for colorectal.
- Main single-run Result/Live view is untouched while the sweep runs.
- `tsc` clean; no behaviour change to existing runs; airgap untouched.