A test pins an origin's labels: `importLabels` and `applyLabelNames` make each name once and attach exactly the remote set #6656

Labels arriving from an origin are matched by name; a re-sync must neither duplicate a label nor leave one the origin removed.

Done:

• [ ] A new test imports labels twice: one row per name
• [ ] applyLabelNames with [a, b] then [b] leaves the issue with only b
• [ ] A name that is blank after trimming is skipped
• [ ] No source file changes unless a case fails; then the pull says which

Files: test/origins-import-labels.test.ts

Risks: label names are compared as the module compares them; read it before asserting case rules.

Before pushing: bun x tsc --noEmit and bun test test/origins-import-labels.test.ts.