[quality] cover match engine gaps: ScoreForRepo, PersistRematchResults, LLMFromEnv (pkg/match 70.5%→85.8%)

[hivecommons-hive]

Test Improvement

Adds pkg/match/engine_gap_test.go covering the previously 0% match-engine functions:

• ScoreForRepo (0% → 100%): fresh score persisted + notified at NotifyThreshold, cache hit with zero gateway traffic, RepoHash invalidation replacing the cached entry in place, append path for a second repo, weak-score notify suppression, and store-error propagation for an unknown idea.
• PersistRematchResults (0% → 100%): happy path persisting TLDR/matches/CNCF with threshold-gated notifications; ErrRepoChanged on stale RepoHash and on a repo missing from the registry (nothing persisted on abort); ErrIdeaChanged on expectedUpdatedAt mismatch.
• LLMFromEnv / envValue (0% → 100%): nil without base URL, trailing-slash trim, DefaultModel fallback, model/key trimming, legacy IDEATE_ prefix fallback per-var, and DIBS_ precedence.
• firstNonEmpty (0% → 100%) and nonHiveCNCF (42.9% → 100%, registry filtering + nil registry).

pkg/match: 70.5% → 85.8%. Test-only; reuses the existing fakeGateway/newFixtures helpers. go vet clean, full go test ./... green.

Disjoint from open PR #145 (which touches only pkg/intake/intake_gap_test.go).

Related Issue

Closes #146

---

Filed by quality agent (hold-gated mode). Human review required.

— hive: agent=quality backend=copilot model=claude-fable-5 copilot=1.0.88

[hivecommons-hive]

Important

Held for human review by the hive's ACMM level gate.

This PR was opened by the "quality" agent while Hive policy required a human checkpoint for that agent. Non-outreach agents are held at ACMM L3–L5; the outreach agent is always held because it publishes project-facing communication.

Hive will automatically remove the hold label once current policy no longer requires a level hold for "quality". If this is an outreach PR, a human must review it and remove the label.

[kubestellar-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign clubanderson for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment