feat(ui): cycle-time percentiles card (p50/p90/p99)

[JSONbored]

Add one analytics card rendering PR review cycle-time percentiles (p50/p90/p99) from the stats feed (src/review/stats.ts StatsPayload). Single percentile-summary card; read-only.

Deliverables

• New CycleTimeCard typed to the relevant fields of StatsPayload (stats.ts:165)
• Three labeled Stat tiles (p50/p90/p99) plus a MiniSparkbar (control-primitives.tsx:149) for the distribution when available
• Loading/empty handling via StateBoundary (state-views.tsx:215)
• Wire into apps/gittensory-ui/src/routes/app.analytics.tsx
• Vitest test covering present percentiles, missing/undefined percentiles (nullish arm), and empty distribution

References

• src/review/stats.ts:165
• src/review/stats.ts:185
• apps/gittensory-ui/src/components/site/control-primitives.tsx:149
• apps/gittensory-ui/src/components/site/state-views.tsx:215

Part of #1967.

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📸 Required: before/after screenshots (this is a UI change)

Non-negotiable. PRs that change UI must include a before/after screenshot table. PRs without it are automatically closed — no exceptions.

Rules:

• Show every page/feature you changed — before and after, one row each.
• Use the markdown table below. Screenshots go inside the table only — no large full-size images pasted elsewhere in the PR.
• Each cell is a clickable thumbnail (a small image linking to the full-size image) with a one-line caption underneath.
• Upload screenshots to the PR by drag-and-drop (GitHub hosts them on its CDN). Do NOT commit image files to the repo.

Copy this and fill it in (replace FULL_IMAGE_URL with the URL GitHub gives you after you drop the image in):

| Page / Feature | Before | After |
|---|---|---|
| `/your-route` | [<img src="FULL_IMAGE_URL" width="260">](FULL_IMAGE_URL)<br><sub>before: short caption</sub> | [<img src="FULL_IMAGE_URL" width="260">](FULL_IMAGE_URL)<br><sub>after: short caption</sub> |

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size: S · held for later release (gittensor:feature once activated)

[linear-code]

JSO-2295