fix: resolve all 40 Svelte dev warnings for clean startup

- Add $state() to 4 reactive variables (guestMode, emailInput, passwordInput, searchInputElement)
- Replace 3 deprecated <svelte:component> with direct component references
- Fix 8 a11y issues: add ARIA roles, tabindex, keyboard handlers to click-handler divs
- Remove 22 unused CSS selectors across 8 shared-ui components

Zero warnings on dev startup.

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

packages/shared-ui/src/command-bar/CommandBar.svelte

@@ -439,13 +439,6 @@
 		border-bottom: 1px solid hsl(var(--color-border));
 	}
 
-	.command-icon {
-		width: 1.25rem;
-		height: 1.25rem;
-		color: hsl(var(--color-muted-foreground));
-		flex-shrink: 0;
-	}
-
 	/* Input with syntax highlighting overlay */
 	.input-highlight-container {
 		position: relative;
@@ -668,13 +661,6 @@
 		text-overflow: ellipsis;
 	}
 
-	.result-favorite {
-		width: 1rem;
-		height: 1rem;
-		color: hsl(var(--color-error));
-		flex-shrink: 0;
-	}
-
 	.quick-actions-list {
 		padding: 0.5rem;
 	}
@@ -699,12 +685,6 @@
 		background: hsl(var(--color-surface-hover));
 	}
 
-	.quick-action-icon {
-		width: 1.25rem;
-		height: 1.25rem;
-		color: hsl(var(--color-muted-foreground));
-	}
-
 	.quick-action span {
 		flex: 1;
 		font-size: 0.9375rem;