Fix/vanish scroll

[TrevorBurgoyne]

Description

• Fix bug where on some browsers, middle-click-drag when annotations were vanished would trigger auto-scroll rather than the normal pan behavior.

PR Checklist

• Merged latest main
• Version number in package.json has been bumped since last release
• Version numbers match between package package.json and src/version.js
• Updated documentation if necessary (currently just in api_spec.md)
• Added changes to changelog.md

Breaking API Changes

No

[Copilot]

Pull request overview

This PR addresses a browser-specific interaction bug where middle-click dragging could trigger the browser’s auto-scroll instead of ULabel’s pan behavior when a subtask is vanished, and adds E2E coverage around zoom/pan behaviors plus CI improvements for Playwright.

Changes:

• Update handle_mouse_down to preventDefault() for drag starts and allow pan/zoom drags even when the subtask is vanished.
• Add a new Playwright E2E spec covering wheel zoom, pan gestures, and vanished-state interaction restrictions.
• Bump version to 0.23.5, update changelog, and add Playwright browser caching in CI.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/e2e/zoom-pan.spec.js	Adds E2E tests for zoom/pan and vanished-state drag behavior.
src/index.js	Adjusts mouse down handling to suppress browser defaults and permit pan/zoom while vanished.
src/version.js	Bumps exported library version to 0.23.5.
package.json	Bumps package version to 0.23.5.
CHANGELOG.md	Adds 0.23.5 release notes entry.
.github/workflows/test.yml	Adds Playwright browser caching to speed up CI runs.