Honor state-specific chord label rotation

Chord labels are standalone Text elements, so the shared label styling path does not carry rotate into emphasis, blur, or select transforms. Reuse the chord rotation calculation for normal labels and only add state rotation overrides when those state labels explicitly configure rotate.

Constraint: Chord node labels are positioned directly on Text rather than through host textConfig.

Rejected: Move chord labels back to host textConfig | would broaden the layout change beyond the review feedback.

Confidence: high

Scope-risk: narrow

Tested: npx jest --config test/ut/jest.config.cjs --runTestsByPath test/ut/spec/series/chord.test.ts --coverage=false

Tested: npx eslint --no-cache src/chart/chord/ChordPiece.ts test/ut/spec/series/chord.test.ts

Tested: npm run checktype