Add minimal stock listing app: actions, Postgres schema, stocks page, Claude Agent SDK harness

- Add stocks table (server/db) with list/get/add/update/delete actions, scoped
  per user, backing both the chat agent and the /stocks UI via
  useActionQuery/useActionMutation
- Add mobile-first /stocks page (shadcn table/cards, watchlist, search) and
  wire it into the sidebar, navigation state, and view-screen context
- Install the platform's Claude Agent SDK harness (server/plugins,
  server/routes/api/claude-agent) so the app agent runs on the platform's own
  Claude subscription instead of the Builder.io gateway; fix the vendored
  turn.post.ts route to resolve the session and wrap it in
  runWithRequestContext, since custom /api/ routes aren't auto-wrapped in
  request context the way /_agent-native/actions/* are
- Add shadcn table/badge/dialog/select components (Tabler icons, not lucide)

actions/delete-stock.ts

@@ -0,0 +1,24 @@
+import { defineAction } from "@agent-native/core/action";
+import { and, eq } from "@agent-native/core/db/schema";
+import { z } from "zod";
+
+import { getDb } from "../server/db/index.js";
+import { stocks } from "../server/db/schema.js";
+
+export default defineAction({
+  description: "Delete a stock listing by id.",
+  schema: z.object({
+    id: z.string().describe("Stock listing id"),
+  }),
+  http: { method: "DELETE" },
+  run: async (args, ctx) => {
+    if (!ctx?.userEmail) throw new Error("Authentication required.");
+    const db = getDb();
+    const deleted = await db
+      .delete(stocks)
+      .where(and(eq(stocks.id, args.id), eq(stocks.ownerEmail, ctx.userEmail)))
+      .returning();
+    if (!deleted[0]) throw new Error("Stock not found.");
+    return { deleted: true, id: args.id };
+  },
+});