test: cover the non-Error rejection and empty-config fallbacks of labelSync, lgtm, mergeQueue and issueComment/approve

[hivecommons-hive]

Test Improvement

Closes the last uncovered branches in four modules (unit coverage on main @ c48bd6d: 98.35% → 98.68% branches; each touched file now 100% branches). No production code changes.

Test file	Covers
__tests__/cronJobTest/labelSync.test.ts	labelSync.ts:48 debug line when no prow config is found; labelSync.ts:107 write() catch when issues.createLabel rejects with a bare string (newOctokit spy-mocked, one label refused, the rest still written, run fails naming kind/bug (offline))
__tests__/label/lgtm.test.ts	lgtm.ts:68 bindLgtm rejecting a non-Error (lgtmBinding spy-mocked): refusal comment carries the string form, no label, setFailed
__tests__/utils/mergeQueue.test.ts	mergeQueue.ts:188 errorMessage() for a non-Error graphql rejection in queueState
__tests__/issueCommentTest/approve.test.ts	approve.ts:94 issue?.user?.login ?? '' — require_self_approval with a payload whose issue has no user is not treated as self-approval

Verified: npx vitest run --coverage → 69 files / 1452 tests pass, thresholds hold; npx eslint clean on the four files.

Disjoint from open hold-gated PRs #217 (auth.test.ts), #219 (tideMergeQueue.test.ts, testUtils.ts), #221 (plugins/approveEvents.test.ts).

Related Issue

Closes #222

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

— hive: agent=quality backend=copilot model=claude-fable-5.1 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.

[hivecommons-hive]

/kind cleanup

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🐝 Hive Agent: quality | Instance: hosted-available-lke648397-260827-5q9t | SHA: c48bd6d

— hive: agent=quality backend=copilot model=claude-fable-5.1 copilot=1.0.88