feat(floating-ai): step 3 — create double-click hook

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

src/renderer/hooks/useDoubleClickAI.ts

@@ -0,0 +1,44 @@
+import { useEffect } from 'react';
+import { useFloatingChat } from '@/context/FloatingChatContext';
+
+// Elements where double-click should NOT trigger the AI popup
+const INTERACTIVE_TAGS = new Set(['INPUT', 'TEXTAREA', 'SELECT']);
+
+export function useDoubleClickAI(): void {
+  const { openAtSection, state } = useFloatingChat();
+
+  useEffect(() => {
+    const handler = (e: MouseEvent) => {
+      const target = e.target as HTMLElement;
+
+      // Skip interactive elements (preserve text selection behavior)
+      if (INTERACTIVE_TAGS.has(target.tagName)) return;
+
+      // Skip contenteditable elements UNLESS they're inside Milkdown
+      if (target.isContentEditable) {
+        const inMilkdown =
+          target.closest('.milkdown-container') ||
+          target.closest('.crepe-editor');
+        if (!inMilkdown) return;
+        // For Milkdown: only trigger if no text was selected by the double-click
+        const selection = window.getSelection();
+        if (selection && selection.toString().trim().length > 0) return;
+      }
+
+      // Walk up DOM to find nearest [data-ai-section]
+      const sectionEl = (target as Element).closest('[data-ai-section]');
+      if (!sectionEl) return;
+
+      const sectionId = sectionEl.getAttribute('data-ai-section');
+      if (!sectionId) return;
+
+      // If popup is already open at THIS section, do nothing
+      if (state.isOpen && state.activeSectionId === sectionId) return;
+
+      openAtSection(sectionId);
+    };
+
+    document.addEventListener('dblclick', handler);
+    return () => document.removeEventListener('dblclick', handler);
+  }, [openAtSection, state.isOpen, state.activeSectionId]);
+}