fix(dialogs): keep pop-ups open when dragging outside

[Go2Engle]

Summary

Selecting text or dragging from inside Find a card or another affected pop-up no longer closes it when the mouse is released outside. Deliberate outside clicks still close the pop-up, and Settings still asks before discarding unsaved changes.

Type of change

• Feature
• Bug fix
• Refactor
• Documentation
• Infrastructure/CI

Technical details

• Share backdrop dismissal handling between the common modal and Settings.
• Require a primary-button gesture to start and end outside the dialog before dismissing it. Check dialog bounds so clicks on empty space or borders inside the pop-up do not close it.
• Clear gesture state after clicks and pointer cancellation, and ignore keyboard or programmatic clicks for backdrop dismissal.
• Add seven regression tests and update the feature reference and card-building workflow guide.

Testing performed

npm test
npm run build
npx prettier --check src/lib/dialog-backdrop.ts tests/dialog-backdrop.test.ts
git diff --check

• All 182 tests passed, and the production build and formatting checks passed.
• Verified in a browser that Find a card stays open after dragging text outside, dragging from outside into the dialog, and clicking its border.
• Verified that outside clicks, Escape, Done, and the close button still close Find a card.
• Verified Settings with a mocked desktop project bridge: dragging text outside does not request dismissal; outside clicks and Escape preserve unsaved edits and show the discard prompt; Keep editing, Discard changes, and outside dismissal with no unsaved changes still work.

Breaking changes

None.

Checklist

• The PR title follows Conventional Commits.
• I ran npm test and npm run build.
• I added regression tests for the behavior change.
• I updated documentation for the user-facing change.
• I reviewed the README summary and screenshots; this bug fix does not change the workflow or interface layout.
• I did not manually edit release versions or CHANGELOG.md.