Fix rotated text anchoring when content changes

[tmchang1258]

Fixes #975

Rysolv bounty: https://rysolv.com/issues/detail/578eaa07-7f66-4d18-a2ea-d68e852c1621

Summary

• Anchor regular Text, BBText, and Bitmap Text renderers around the object origin instead of the rendered center that changes with text width.
• Preserve horizontal alignment offsets for wrapped text while keeping the rotation pivot stable.
• Align editor renderer center calculations with the runtime pivot/hitbox behavior.
• Add a Pixi runtime regression test for rotated text staying anchored after content changes.

Validation

• npm run build from GDJS
• npm run check-types from GDJS
• npm run test:chromeHeadlessNoSandbox from GDJS/tests (1182 executed, 12 skipped, success)
• npx prettier --check on the touched source and test files
• git diff --check

Note

npm run check-format currently reports many pre-existing formatting differences across the repo. The files touched in this PR pass a targeted Prettier check.