various fixes

browser-extension/content.js

@@ -23,7 +23,9 @@
 
   // ── Extension→Page messaging (capture context for the popup) ──────────────
   browser.runtime.onMessage.addListener(function (msg) {
-    if (msg && msg.kind === 'get_context') {
+    if (!msg || typeof msg.kind !== 'string') return Promise.resolve(undefined);
+
+    if (msg.kind === 'get_context') {
       var selection = '';
       try { selection = window.getSelection().toString().trim(); } catch (e) {}
       return Promise.resolve({
@@ -32,6 +34,26 @@
         url: window.location.href || '',
       });
     }
+
+    if (msg.kind === 'get_viewport') {
+      var ph = Math.max(
+        document.documentElement ? document.documentElement.scrollHeight : 0,
+        document.body ? document.body.scrollHeight : 0
+      );
+      return Promise.resolve({
+        viewportWidth: window.innerWidth || document.documentElement.clientWidth || 0,
+        viewportHeight: window.innerHeight || document.documentElement.clientHeight || 0,
+        pageHeight: ph,
+        devicePixelRatio: window.devicePixelRatio || 1,
+        scrollY: window.scrollY || window.pageYOffset || 0,
+      });
+    }
+
+    if (msg.kind === 'scroll_to') {
+      window.scrollTo(0, msg.y);
+      return Promise.resolve({ y: window.scrollY || window.pageYOffset || 0 });
+    }
+
     return Promise.resolve(undefined);
   });
 })();