Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

packages/core/locals.d.ts

@@ -0,0 +1,41 @@
+/**
+ * EmDash Astro type declarations
+ *
+ * Augments App.Locals with EmDash types.
+ * Referenced via triple-slash directive in the generated emdash-env.d.ts.
+ */
+
+import type { User } from "@emdash-cms/auth";
+
+import type { EmDashHandlers } from "./dist/types.d.mts";
+
+declare global {
+	namespace App {
+		interface Locals {
+			/**
+			 * EmDash API handlers - available on /_emdash/* routes
+			 */
+			emdash: EmDashHandlers;
+
+			/**
+			 * Authenticated user - set by auth middleware when a valid session exists
+			 */
+			user?: User;
+
+			/**
+			 * Per-session Durable Object database for playground mode.
+			 *
+			 * Set by the playground middleware (@emdash-cms/cloudflare). Read by
+			 * the runtime middleware and request-context middleware to set the
+			 * database in ALS for the current request.
+			 *
+			 * This exists because Vite SSR loads two copies of request-context.ts
+			 * (dist for integration middleware, source for the loader). locals
+			 * bridges the DB across that module boundary.
+			 */
+			__playgroundDb?: unknown;
+		}
+	}
+}
+
+export {};