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/plugin.json

@@ -0,0 +1,10 @@
+{
+    "name": "watch",
+    "version": "1.0.0",
+    "description": "Analog clock overlay. Shows after 5 min idle or press W.",
+    "frontend": {
+        "js": ["watch.js"],
+        "css": ["watch.css"],
+        "html": ["watch.html"]
+    }
+}