feat(floating-ai): step 8 — page interactions (all variants)

Register AI sections across all content pages with dual-anchor scroll
tracking, cross-page navigation via [SECTION:xxx] tags, and right-margin
positioning for the notes editor.

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

src/renderer/hooks/useDoubleClickAI.ts

@@ -5,7 +5,7 @@ import { useFloatingChat } from '@/context/FloatingChatContext';
 const INTERACTIVE_TAGS = new Set(['INPUT', 'TEXTAREA', 'SELECT']);
 
 export function useDoubleClickAI(): void {
-  const { openAtSection, state } = useFloatingChat();
+  const { openAtSection, moveToSection, sections, state } = useFloatingChat();
 
   useEffect(() => {
     const handler = (e: MouseEvent) => {
@@ -35,10 +35,20 @@ export function useDoubleClickAI(): void {
       // If popup is already open at THIS section, do nothing
       if (state.isOpen && state.activeSectionId === sectionId) return;
 
-      openAtSection(sectionId);
+      // Build opts for right-margin sections
+      const section = sections.get(sectionId);
+      const opts = section?.anchorMode === 'right-margin' ? { clickY: e.clientY } : undefined;
+
+      // If chat is already open at a different section, move (keep conversation)
+      if (state.isOpen) {
+        moveToSection(sectionId, opts);
+        return;
+      }
+
+      openAtSection(sectionId, opts);
     };
 
     document.addEventListener('dblclick', handler);
     return () => document.removeEventListener('dblclick', handler);
-  }, [openAtSection, state.isOpen, state.activeSectionId]);
+  }, [openAtSection, moveToSection, sections, state.isOpen, state.activeSectionId]);
 }