feat: improve quality docs and virtual scroll

[yeyunwen]

Summary

• improve engineering baseline with package-level typecheck scripts, CI lint/typecheck/test/docs build steps, Vue SFC shims, and ignore rules
• align README/API docs with source, unify MIT/license and Node 24 guidance, and add FAQ troubleshooting docs
• clean React/Vue components, add safe React hook methods and data-change timer cleanup
• add explicit virtual scroll controls (virtual, virtualThreshold) and clarify fixed-size vs experimental dynamic-size behavior
• add core behavior tests for scroll lifecycle, force scrolling, destroy cleanup, virtual modes, ranges, and dynamic size prediction
• add React/Vue component and hook smoke tests for render, empty state, click callbacks, ref/expose methods, virtual rendering, and data-change cleanup
• add coverage scripts/config for core/react/vue with coverage reports over behavior source files
• add AGENTS.md and .agents/code-review.md to document Agent collaboration rules and mandatory PR self-review checks

Coverage

• @seamless-scroll/core: statements 98.03%, branches 93.24%, functions 100%, lines 98.03%
• @seamless-scroll/react: statements 98.87%, branches 90.84%, functions 100%, lines 98.87%
• @seamless-scroll/vue: statements 96.89%, branches 93.49%, functions 100%, lines 96.89%

Validation

• pnpm test:coverage
• pnpm test
• pnpm lint
• pnpm typecheck
• pnpm build
• pnpm docs:build
• pnpm install --frozen-lockfile --offline
• git diff --check

Notes

• Existing local dependency catalog updates remain preserved separately in stash@{0}: On main: wip: pnpm catalog dependency updates and were not applied.
• docs:build completes with existing VitePress/demo-plugin browser externalization warnings for path/fs, Dart Sass legacy JS API deprecation warnings, and chunk-size warning.
• pnpm install --frozen-lockfile --offline completes with pnpm warning that esbuild build scripts are ignored unless approved.
• Before updating this PR, the .agents/code-review.md checklist was applied.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@seamless-scroll/core@9

npm i https://pkg.pr.new/@seamless-scroll/react@9

npm i https://pkg.pr.new/@seamless-scroll/shared@9

npm i https://pkg.pr.new/@seamless-scroll/vue@9

commit: f44d464