fix(widget): keep chat history rows scrollable

[happykawayigt]

Summary

• prevent chat drawer headers, the new-chat action, and conversation rows from shrinking
• rebuild the committed widget bundle from the TypeScript source
• add a browser regression test that verifies stable row heights and vertical overflow with 30 conversations

Fixes #61.

Validation

• npm run typecheck:widget
• npm run typecheck:e2e
• npm run test:widget
• npm run build:widget
• npx playwright test tests/e2e/widget.spec.ts --headed (21 passed)
• git diff --check origin/main...HEAD

AI assistance

AI assistance was used to inspect the drawer layout, implement the focused CSS fix and regression test, and run validation. The final diff and test behavior were reviewed before submission.

[AmitAvital1]

Hi please attach UI screenshot :)