#580 [Bug Fix] Dialog: only dismiss on clicks outside the panel (#570)

Closes #570

Problem

DialogContent is the native <dialog> itself, with p-6 gap-4. backdropClick dismissed on any click whose target was the <dialog>, but clicks on the panel's own padding and on the gaps between children report the same target as a click on ::backdrop. So clicking inside the panel, between two fields, closed the dialog.

A related case: selecting text inside the dialog and releasing the mouse outside it also fires click on the <dialog>, which closed it mid-selection.

Fix

• dialog_controller.js: a new backdropPointerdown records whether the press started outside the panel's rect. backdropClick dismisses only when the press both started and ended outside it.
• dialog_content.rb: data-action now also wires pointerdown->ruby-ui--dialog#backdropPointerdown.
• mcp/data/registry.json rebuilt (rake mcp:build).

No markup or API change, so docs/app/views/docs/dialog.rb is unchanged. I kept the panel as the <dialog> instead of moving to a shadcn-style inner wrapper, which would change the DOM that users customize.

Testing

• cd gem && bundle exec rake: 298 runs, 0 failures. standardrb: no offenses. Added a regression test for the pointerdown action.
• Browser: the dialog was rendered by the gem and driven with real CDP mouse events in headless Chrome, against main's controller and this branch's:

Scenario	main	This PR
Click on panel padding	closes (bug)	stays open
Click in gap between inputs	closes (bug)	stays open
Select text, drag outward, release	closes (bug)	stays open
Press on backdrop, release inside	n/a	stays open
Click on backdrop	closes	closes

To test manually: open any Dialog on the docs site, click in the padding or between two fields (it should stay open), then click the backdrop (it should close).

Note

#517 (exit animation) also edits backdropClick. Whichever PR merges second gets a small conflict in that one method.

🤖 Generated with Claude Code

---

Summary by cubic

Brings the dialog to shadcn Base UI + vega parity and fixes clicks on the panel's own padding and gaps dismissing it — those report the <dialog> as target, same as backdrop clicks, so a press now counts as a backdrop click only when it both starts and ends outside the panel's rect. Dragged text selections that release outside no longer close the dialog either.

• Vega classes for the panel, ::backdrop overlay, header, footer, and title (now <h2>); explicit size: is unchanged and the default width is now max-w-md at sm+.
• DialogContent(show_close_button:) toggles the corner close button; DialogFooter(show_close_button:) adds a footer Close button.
• Open and close animate off data-state; Esc, backdrop, and the close buttons play the exit animation before close(), with motion-reduce support.
• The controller names the dialog from its title/description (aria-labelledby/aria-describedby) and sets aria-haspopup/aria-controls/aria-expanded on triggers.