fix(dialog): align HA settings form shell (#609)

Use Home Assistant's public dialog tokens for the reviewed 560 px canvas, height cap, single scroller and mobile fullscreen layout. Keep generic dialogs and the native fallback unchanged, with authentic-HA evidence and mutation witnesses.

Issue: #609
User-Visible: yes

test/form-shell-consumers.test.mjs

@@ -0,0 +1,18 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+
+const consumers = [
+  ['space', 'src/editors/space-settings-dialog.ts'],
+  ['settings', 'src/editors/general-settings-dialog.ts'],
+  ['room', 'src/editors/room-settings-dialog.ts'],
+  ['marker', 'src/editors/marker-dialog.ts'],
+  ['onboarding', 'src/houseplan-onboarding-runtime.ts'],
+];
+
+test('#609 all five settings consumers opt into the shared form shell', () => {
+  for (const [kind, file] of consumers) {
+    const source = readFileSync(new URL(`../${file}`, import.meta.url), 'utf8');
+    assert.match(source, new RegExp(`data-kind=["']${kind}["'][^>]*form-shell`), file);
+  }
+});