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

[claytonlin1110]

Summary

• Add cycleTime (p50/p90/p99 + histogram distribution) to StatsPayload via computeCycleTimeAggregate, reading paired gate_decision → pr_outcome rows from review_audit.
• Surface cycleTime on the operator dashboard payload and render a new read-only CycleTimeCard on /app/analytics with three percentile Stat tiles and a MiniSparkbar when distribution data is present.
• Vitest coverage for present percentiles, nullish percentile formatting, empty distribution, and fail-safe empty aggregates.

Scope

• The PR title follows type(scope): short summary Conventional Commit format, for example fix(api): restore profile access checks.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked a currently open issue this PR resolves (e.g. Closes #123) — a linked open issue is required for every contributor PR.

Closes #2194

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; codecov/patch requires ≥99% coverage of the lines AND branches you changed (aim for 100% on your diff so CI variance does not fail near the threshold). Global coverage is a non-blocking trend with a loose 90% backstop, not the gate.
• npm run test:workers
• npm run build:mcp
• npm run test:mcp-pack
• npm run ui:openapi:check
• npm run ui:lint
• npm run ui:typecheck
• npm run ui:build
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

If any required check was skipped, explain why:

• Full npm run test:ci gate pending CI; targeted unit/UI tests and coverage run locally on changed paths.

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• Auth, cookie, CORS, GitHub App, Cloudflare, or session changes include negative-path tests.
• API/OpenAPI/MCP behavior is updated and tested where needed.
• UI changes use live API data or real empty/error/loading states, not production mock/demo fallbacks.
• Visible UI changes include a UI Evidence section below with JPG/JPEG or PNG screenshots arranged as organized, captioned, clickable thumbnails. SVG screenshots are not used as review evidence. Review-only screenshots or recordings are not committed to the repository.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

UI Evidence

Page / Feature	Before	After
/app/analytics	before: analytics page without cycle-time card	after: Review cycle time card with p50/p90/p99 + distribution

Screenshots to be uploaded to the PR (drag-and-drop) and URLs substituted above before merge.

Test plan

• npm run test -- test/unit/stats.test.ts test/unit/operator-dashboard.test.ts
• npm run test -- src/components/site/app-panels/cycle-time-card.test.tsx (UI)
• Confirm /app/analytics shows empty state when no paired audit rows exist
• Confirm percentile tiles populate when review_audit has gate_decision + pr_outcome pairs

Notes

• Mirrors the feat(ui): gate-precision analytics card (precision + confusion matrix) #2191 gate-precision card pattern: backend aggregate on the operator dashboard, UI model + card + Vitest.

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.02%. Comparing base (a26924a) to head (0867714).
⚠️ Report is 13 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4468   +/-   ##
=======================================
  Coverage   94.01%   94.02%           
=======================================
  Files         418      418           
  Lines       37439    37469   +30     
  Branches    13685    13692    +7     
=======================================
+ Hits        35200    35230   +30     
  Misses       1583     1583           
  Partials      656      656           

Files with missing lines	Coverage Δ
src/review/stats.ts	99.08% <100.00%> (+0.34%)	⬆️
src/services/operator-dashboard.ts	100.00% <ø> (ø)

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Warning

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⏸️ Gittensory review result - manual review recommended

_{Review updated: 2026-07-09 20:57:48 UTC}

8 files · 1 AI reviewer · no blockers · readiness 100/100 · CI green · clean

⏸️ Suggested Action - Manual Review

• Touches a guarded path — held for manual review: This PR changes guardrail-protected path(s): src/services/operator-dashboard.ts (matched src/services/**).

Review summary
Adds computeCycleTimeAggregate (src/review/stats.ts) to compute p50/p90/p99 cycle-time percentiles + a histogram from paired gate_decision/pr_outcome review_audit rows, wires it fail-safe into StatsPayload and the operator-dashboard payload, and renders a new read-only CycleTimeCard on /app/analytics. The pure fold logic and D1 wrapper are correct and well-tested (present/nullish/empty/fail-safe/day-clamp branches all covered), no schema change is needed since it only reads existing review_audit rows, and the diff is scoped to issue #2194 with no unrelated changes bundled in.

Nits — 6 non-blocking

• src/review/stats.ts:~223-236 (CYCLE_TIME_SQL): the ROW_NUMBER()-latest gate_decision per target_id isn't scoped by `source` the way computeGateEval (src/review/parity.ts) optionally is — once a SHADOW writer is active, review_audit can hold gate_decision rows from two sources for the same target_id, and this query could pick whichever one has the later created_at, mixing authoritative and shadow decision timestamps into decided_at; consider adding the same optional `source` filter computeGateEval uses before a shadow writer goes live.
• src/review/stats.ts: the `days` clamp (`Number.isFinite(opts.days) && opts.days > 0 ? Math.min(opts.days, 730) : 90`) is duplicated verbatim between computeCycleTimeAggregate and computeStats; a small shared helper would remove the duplication, though it's harmless as-is.
• CYCLE_TIME_SQL filters `pr_outcome.created_at >= fromIso` in addition to `gate_decision.created_at >= fromIso`; since an outcome always follows its decision, the po filter is logically redundant given the gd filter already excludes those rows — not a bug, just worth a one-line comment or removal for clarity.
• Scope CYCLE_TIME_SQL's gate_decision CTE by `source` (mirroring computeGateEval's optional param in src/review/parity.ts) so cycle-time numbers stay meaningful once a shadow writer is active.
• Factor the repeated day-clamp expression (src/review/stats.ts, both computeCycleTimeAggregate and computeStats) into a small shared `clampDays(days, max=730, default=90)` helper.
• Touches a guarded path — held for manual review — A maintainer must review and merge this change.

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	✅ Linked	#2194
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 450 registered-repo PR(s), 312 merged, 104 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	claytonlin1110; Gittensor profile; 450 PR(s), 104 issue(s).
Gate result	⚠️ Not blocking	Advisory; not blocking this PR.

Linked issue satisfaction

Partially addressed
The PR delivers the CycleTimeCard with typed p50/p90/p99 Stat tiles, a conditional MiniSparkbar, wiring into app.analytics.tsx, and Vitest coverage for present/nullish/empty-distribution cases as required, but it implements its own inline hasSamples/empty-state branching instead of using the explicitly specified StateBoundary component (state-views.tsx:215) for loading/empty handling, leaving that

Review context

• Author: claytonlin1110
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 450 PR(s), 104 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

Visual preview

Route	Viewport	Before (production)	After (this PR's preview)	Diff
/app/analytics	desktop	—		—
/app/analytics	mobile	—		—

Click any thumbnail to open the full-size screenshot. Before = production · After = this PR's preview deploy.

_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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