feat: implement Stories 3.4, 3.5, 3.6 — AI proposals, wizard, hover & palette

Story 3.4: AI semantic suggestions with accept/reject workflow
- ProposalBar overlay with visual diff
- Accept/reject flow with graph snapshot restore
- useProposalDiff hook for change summary
- System prompt scoping for selected elements

Story 3.5: New diagram wizard with AI type inference
- CreateDiagramDialog with AI type inference (Haiku)
- initialDescription prop for chat-first flow
- Auto-send on mount with hasSentInitial ref guard
- DB migration for diagram description column

Story 3.6: Hover affordances and command palette
- HoverAffordances toolbar (5 AI actions, debounced)
- CommandPalette (Cmd+K) with AI, nav, Go to Node
- prefillChat/fitViewRequested/focusNodeId actions
- Code review: getNodesBounds, onOpenRightPanel,
  timer cleanup, test count fix

374 tests passing (251 web + 123 AI).

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

apps/web/src/modules/copilot/hooks/useGraphMutation.ts

@@ -23,6 +23,41 @@ interface GraphPatchData {
   groups?: GraphData["groups"];
 }
 
+function patchToGraphData(patch: GraphPatchData, fallbackType: DiagramType): GraphData {
+  const effectiveDiagramType =
+    (patch.meta.diagramType as DiagramType) ?? fallbackType;
+
+  return {
+    meta: {
+      version: patch.meta.version ?? "1",
+      title: patch.meta.title,
+      diagramType: effectiveDiagramType,
+      layoutDirection: patch.meta.layoutDirection,
+      edgeRouting: patch.meta.edgeRouting,
+    },
+    nodes: patch.nodes,
+    edges: patch.edges,
+    pools: patch.pools,
+    groups: patch.groups,
+  };
+}
+
+export function persistGraphData(diagramId: string, graphData: GraphData) {
+  api.diagrams[":id"]
+    .$patch({
+      param: { id: diagramId },
+      json: { graphData: graphData as unknown as Record<string, unknown> },
+    })
+    .then((res) => {
+      if (!res.ok) {
+        toast.error("Failed to save diagram — changes may be lost on reload");
+      }
+    })
+    .catch(() => {
+      toast.error("Failed to save diagram — changes may be lost on reload");
+    });
+}
+
 export function useGraphMutation(diagramId: string, diagramType: DiagramType) {
   const setNodes = useGraphStore((s) => s.setNodes);
   const setEdges = useGraphStore((s) => s.setEdges);
@@ -32,23 +67,7 @@ export function useGraphMutation(diagramId: string, diagramType: DiagramType) {
 
   const applyGraphPatch = useCallback(
     (patch: GraphPatchData) => {
-      const effectiveDiagramType =
-        (patch.meta.diagramType as DiagramType) ?? diagramType;
-
-      const graphData: GraphData = {
-        meta: {
-          version: patch.meta.version ?? "1",
-          title: patch.meta.title,
-          diagramType: effectiveDiagramType,
-          layoutDirection: patch.meta.layoutDirection,
-          edgeRouting: patch.meta.edgeRouting,
-        },
-        nodes: patch.nodes,
-        edges: patch.edges,
-        pools: patch.pools,
-        groups: patch.groups,
-      };
-
+      const graphData = patchToGraphData(patch, diagramType);
       const { nodes, edges } = graphToFlow(graphData);
 
       setNodes(nodes);
@@ -62,21 +81,7 @@ export function useGraphMutation(diagramId: string, diagramType: DiagramType) {
       }
 
       requestLayout();
-
-      // Persist graphData to database (fire-and-forget with error reporting)
-      api.diagrams[":id"]
-        .$patch({
-          param: { id: diagramId },
-          json: { graphData: graphData as unknown as Record<string, unknown> },
-        })
-        .then((res) => {
-          if (!res.ok) {
-            toast.error("Failed to save diagram — changes may be lost on reload");
-          }
-        })
-        .catch(() => {
-          toast.error("Failed to save diagram — changes may be lost on reload");
-        });
+      persistGraphData(diagramId, graphData);
     },
     [
       diagramId,
@@ -89,5 +94,13 @@ export function useGraphMutation(diagramId: string, diagramType: DiagramType) {
     ],
   );
 
-  return { applyGraphPatch };
+  const proposeGraphPatch = useCallback(
+    (patch: GraphPatchData) => {
+      const graphData = patchToGraphData(patch, diagramType);
+      useGraphStore.getState().proposeChanges(graphData);
+    },
+    [diagramType],
+  );
+
+  return { applyGraphPatch, proposeGraphPatch };
 }