test: add watch HMR platform CI coverage

[sonofmagic]

Summary

• add platform-derived watch-HMR cases for Taro and uni-app mini-program outputs
• keep base watch case names as default platform aliases
• update e2e-watch PR/nightly matrices with representative and full platform coverage

Testing

• pnpm --filter weapp-tailwindcss exec vitest run test/watch-hmr-regression.unit.test.ts test/watch-hmr-coverage-matrix.unit.test.ts --coverage.enabled=false
• E2E_FRAMEWORK_SUPPORT=1 pnpm exec vitest run -c ./e2e/vitest.e2e.config.ts e2e/framework-ci-support.test.ts e2e/e2e-matrix.test.ts --coverage.enabled=false
• git diff --check

Notes

• pnpm typecheck currently fails on unrelated existing strict TypeScript errors in package source files.
• local full live watch smoke was not completed; Taro Alipay hit local environment/runtime failures.

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