Add tests for Dialog and Tooltip, raise components/ui threshold to 93%

Dialog: open/close lifecycle, cancel event handling, DialogHeader.
Tooltip: show on pointer enter, hide on pointer leave. Raises
components/ui coverage threshold to enforce testing of future
primitives.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vitest.config.ts

@@ -34,8 +34,8 @@ export default defineConfig({
 					branches: 55,
 				},
 				"apps/web/src/components/ui": {
-					lines: 86,
-					branches: 83,
+					lines: 93,
+					branches: 90,
 				},
 			},
 		},