watch plugin: analog clock overlay with SVG watchface

Simple watchface with second-hand wobble animation, 5-min idle
auto-show, W key toggle, light/dark theme colors, backdrop blur
from theme settings. Grace period prevents instant dismiss.

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

public/plugins/watch/watch.html

@@ -0,0 +1,13 @@
+<div id="watch-overlay" class="hidden" aria-hidden="true">
+    <div id="watch-darkening"></div>
+    <div id="watch-analog">
+        <div id="watch-dial">
+            <div id="watch-layer-digits" class="watch-layer"></div>
+            <div id="watch-layer-hour" class="watch-layer"></div>
+            <div id="watch-layer-minute" class="watch-layer"></div>
+            <div id="watch-layer-second" class="watch-layer">
+                <div id="watch-second-wobble"></div>
+            </div>
+        </div>
+    </div>
+</div>