feat(ui): 15-point UX overhaul — affordances, feedback, and navigation

Address friction points identified in a full interface audit:
- Re-add status badge to dashboard tiles so run state is visible at a glance
- Add active nav indicator and SSE connection health monitor (live/stale)
- Show manual registration form by default instead of hiding behind <details>
- Add copy-to-clipboard buttons on SSH hold command and quick-register one-liner
- Replace tooltip-only profile descriptions with inline visible text
- Clarify non-destructive toggle with explicit stage impact description
- Replace disabled "Start vetting" button with actionable offline guidance
- Swap browser confirm() dialogs for styled inline confirmations
- Add colored badge to spec diffs summary visible when collapsed
- Add distinct "cancelled" mood for cancelled runs (vs idle)
- Add match count to log search and aria-label for accessibility
- Add styled 404 page rendered inside the app shell

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/web/templates/host_tile.templ

@@ -16,7 +16,7 @@ import (
 templ HostTile(t TileData) {
 	<article
 		id={ fmt.Sprintf("host-%d", t.Host.ID) }
-		class="tile"
+		class={ "tile", "tile-" + tileMood(t.Latest) }
 		sse-swap={ fmt.Sprintf("tile-%d", t.Host.ID) }
 		hx-swap="outerHTML"
 	>
@@ -25,6 +25,11 @@ templ HostTile(t TileData) {
 			<div class="tile-name">{ t.Host.Name }</div>
 			<span class={ "tile-last-seen", lastSeenClass(t.LastSeenAt) }>{ lastSeenLabel(t.LastSeenAt) }</span>
 		</header>
+		if t.Latest != nil {
+			<div class="tile-status">
+				<span class={ "run-status-badge", "run-status-badge-sm", "run-status-" + tileMood(t.Latest) }>{ tileStatus(t.Latest) }</span>
+			</div>
+		}
 	</article>
 }
 
@@ -84,7 +89,9 @@ func tileMood(r *model.Run) string {
 		return "pass"
 	case model.StateFailed, model.StateFailedHolding:
 		return "fail"
-	case model.StateReleased, model.StateCancelled:
+	case model.StateCancelled:
+		return "cancelled"
+	case model.StateReleased:
 		return "idle"
 	}
 	return "active"