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>

packages/api/src/modules/ai/copilot/router.ts

@@ -3,6 +3,7 @@ import * as z from "zod";
 
 import { getCopilotHistory, streamCopilot } from "@turbostarter/ai/copilot/api";
 import { copilotMessageSchema } from "@turbostarter/ai/copilot/schema";
+import { inferDiagramType } from "@turbostarter/ai/copilot/type-inference";
 
 import { enforceAuth, deductCredits, rateLimiter, validate } from "../../../middleware";
 
@@ -12,6 +13,10 @@ const chatIdQuerySchema = z.object({
   chatId: z.string(),
 });
 
+const inferTypeSchema = z.object({
+  description: z.string().min(3).max(500),
+});
+
 export const copilotRouter = new Hono<{
   Variables: {
     user: User;
@@ -27,6 +32,17 @@ export const copilotRouter = new Hono<{
       return c.json(messages);
     },
   )
+  .post(
+    "/infer-type",
+    enforceAuth,
+    rateLimiter,
+    validate("json", inferTypeSchema),
+    async (c) => {
+      const { description } = c.req.valid("json");
+      const result = await inferDiagramType(description);
+      return c.json(result);
+    },
+  )
   .post(
     "/",
     enforceAuth,

packages/api/src/modules/diagram/router.ts

@@ -24,12 +24,14 @@ export const createDiagramSchema = z.object({
     "sequence",
     "flowchart",
   ]),
+  description: z.string().max(500).optional(),
   projectId: z.string().optional(),
 });
 
 export const updateDiagramBodySchema = z
   .object({
     title: z.string().min(1).max(255).optional(),
+    description: z.string().max(500).optional(),
     projectId: z.string().nullable().optional(),
     sortOrder: z.number().int().min(0).optional(),
     graphData: z
@@ -45,6 +47,7 @@ export const updateDiagramBodySchema = z
   .refine(
     (data) =>
       data.title !== undefined ||
+      data.description !== undefined ||
       data.projectId !== undefined ||
       data.sortOrder !== undefined ||
       data.graphData !== undefined,