Test the packed lib/ in vp run ci

[nstepien]

Tests now import react-data-grid instead of relative src paths, so vp run ci can run them against the packed lib/, which is what we publish.

• vp test / vp run test alias react-data-grid to src/index.ts with test.alias, so day-to-day testing doesn't need vp pack.
• vp run ci runs its tests with TEST_LIB=true, which drops the alias and loads lib/styles.css as a setup file. TEST_LIB is in the test task's cache env, so src/ and lib/ results are cached separately.
• TEST_LIB is separate from CI, so vp run test test/visual --update in the screenshot workflow, which doesn't pack, keeps testing src/. Visual tests are still enabled by CI alone.
• tsconfig.test.json maps react-data-grid to src/index.ts, since vp run typecheck runs before vp pack.

A few tests still import internal classnames that aren't public (src/style/cell, src/style/row, src/HeaderRow). They compiled with the root ecij() plugin's default css- prefix, while lib/ uses rdg-<version>-, so 63 tests failed against lib/. The root plugin now shares classPrefix with vp pack; as a side effect, the website also gets rdg-<version>- classes.

AGENTS.md notes that vp run ci tests lib/ while vp test tests src/.

Verified locally: vp run ci (544 passed, 3 skipped against lib/) and vp test (544 passed, 3 skipped against src/). Visual tests only run in CI.

🤖 Generated with Claude Code

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.24%. Comparing base (f7d4e27) to head (0af0242).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #4209       +/-   ##
==========================================
- Coverage   98.41%   3.24%   -95.17%     
==========================================
  Files          45      45               
  Lines        1951    1851      -100     
  Branches      727     637       -90     
==========================================
- Hits         1920      60     -1860     
- Misses         31    1791     +1760     

see 43 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[nstepien]

Cool idea, but it doesn't work well with code coverage