feat(engine): add pickTopMetadataOpportunities helper

[kiannidev]

Summary

• Add pickTopMetadataOpportunities(candidates, context, limit) to @jsonbored/gittensory-engine: ranks metadata discovery candidates via rankMetadataOpportunities, then returns the top N entries.
• Non-finite or negative limits fail closed to an empty list; limit is truncated to a non-negative integer.
• Implemented in new metadata-top-pick.ts (separate from the v8-ignored metadata heuristics module) and exported from the package barrel.

Why no linked issue

Complements the merged pickTopRankedOpportunities helper (#3328) for the metadata discovery path — miners fanning out issue metadata can cap results without re-slicing ranked output or reimplementing limit sanitization.

Conflict avoidance

Touches only packages/gittensory-engine/src/metadata-top-pick.ts (new file), packages/gittensory-engine/src/index.ts (one export line), and test/unit/opportunity-metadata-signals.test.ts. No overlap with open PRs (#3314 miner CLI, #3322 enrichment, #3315/#3255 queue, #3316 signals, #3304 review holds, grafana/docs PRs).

Codecov patch

Vitest covers every branch (top-N slice, miner-disabled filtering, zero/negative/non-finite limits, empty input, barrel export). Local diff-cover reports 100% patch coverage on metadata-top-pick.ts.

Test plan

• npm run build --workspace @jsonbored/gittensory-engine
• npm run build:miner
• npx vitest run test/unit/opportunity-metadata-signals.test.ts (25 tests)
• diff-cover coverage/lcov.info --compare-branch=main --fail-under=99 → 100%
• CI validate / validate-code / codecov patch+project / orb review agent

[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 93.88%. Comparing base (c556d78) to head (6bdca99).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3331   +/-   ##
=======================================
  Coverage   93.87%   93.88%           
=======================================
  Files         277      278    +1     
  Lines       30522    30526    +4     
  Branches    11114    11116    +2     
=======================================
+ Hits        28654    28658    +4     
  Misses       1211     1211           
  Partials      657      657           

Files with missing lines	Coverage Δ
...ackages/gittensory-engine/src/metadata-top-pick.ts	100.00% <100.00%> (ø)

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[gittensory-orb]

Warning

🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨🟨

⏸️ Gittensory review result - manual review recommended

_{Review updated: 2026-07-05 03:48:46 UTC}

3 files · 1 AI reviewer · no blockers · readiness 55/100 · CI green · clean

⏸️ Suggested Action - Manual Review

Review summary
The AI review returned non-blocking notes for this change but did not include a separate narrative summary. Review the nits below before deciding this PR.

Nits — 3 non-blocking

• nit: test/unit/opportunity-metadata-signals.test.ts:144 exercises zero, negative, NaN, and empty input, but it does not assert the documented fractional-limit truncation behavior driven by packages/gittensory-engine/src/metadata-top-pick.ts:17.
• Add a focused assertion such as pickTopMetadataOpportunities(candidates, { nowMs: NOW }, 1.9) returning exactly one entry so the Math.trunc contract in packages/gittensory-engine/src/metadata-top-pick.ts:17 is locked down.
• Readiness score is below the configured threshold — Use the readiness panel as advisory maintainer context; the score does not block this PR.

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	⚠️ Missing	No linked issue or no-issue rationale found.
Related work	⚠️ 3 scoped overlaps	Top overlaps are listed below; lower-confidence bulk is hidden.
Change scope	❌ 8/20	High review scope from cached public metadata (no linked issue context).
Validation posture	❌ 5/25	Preflight is holding this PR: the review lane is unavailable, so it is not ready for automated review.
Contributor workload	✅ 10/10	Author activity: 1334 registered-repo PR(s), 648 merged, 49 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	kiannidev; Gittensor profile; 1334 PR(s), 49 issue(s).
Gate result	✅ Passing	No configured blocker found.

Review context

• Author: kiannidev
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository registration is not available in the local Gittensory cache.
• Public profile languages: TypeScript, MDX, C++, HTML, Rust
• Official Gittensor activity: 1334 PR(s), 49 issue(s).
• Related work: Titles/paths share 10 meaningful terms. (issue #2276, issue #2281)
• Related work: Titles/paths share 8 meaningful terms. (issue #2276, issue #2287)
• Related work: Titles/paths share 8 meaningful terms. (issue #2287, issue #2281)

Contributor next steps

• Explain no-issue PR.
• Review top overlaps.
• Add a concise scope and risk note.
• Await review-lane availability.
• Refresh registry data or choose a registered active repo.
• Link the issue being solved, or explicitly explain why this is a no-issue PR.
• Check active issues and PRs before submitting.

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.

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

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• Re-run Gittensory review

[gittensory-orb]

Gittensory approves — the gate is satisfied and CI is green.