fix(labels): ensurePullRequestLabel misses labels beyond first page

[glorysr1209-png]

Summary

Closes #160.

Look up repository labels by name instead of scanning only the first labels page.

Changes

• GET /repos/{owner}/{repo}/labels/{name} with 404 → create when allowed.
• Update label unit tests for direct lookup.

Test plan

• npm test -- test/unit/github-labels.test.ts

[JSONbored]

@glorysr1209-png The direct label lookup is a good API-level fix, but the branch currently breaks webhook accounting.

A few notes:

• Switching to GET /labels/{name} avoids the first-page-only repository-label lookup problem.
• CI now fails because the queue webhook test expected labelsCreated: 1 and received labelsCreated: 0.
• That means the missing-label creation path is no longer reflected correctly in the visible queue stats.

Required changes:

• Preserve direct lookup for existing labels.
• Preserve missing-label creation and labelsCreated accounting when the label does not exist.
• Keep both cases covered in tests.

Validation expected:

• npm run test:coverage

[JSONbored]

@glorysr1209-png this is still blocked by CI.

A few notes:

• Direct label lookup by name is a reasonable fix for first-page pagination misses.
• Current validate fails in test/unit/queue.test.ts because labelsCreated is 0 where the test expects 1.
• The body needs current validation/safety evidence.

Required changes:

• Fix the label-create/lookup behavior or update the test only if the expected behavior has intentionally changed.
• Update the PR body to the current template.

Validation expected:

• Focused label tests
• Full validate pipeline

[JSONbored]

This is now stale/have been awaiting changes for a few days with no response. Please feel free to try again based on current codebase status if interested.