Merge origin/master (goal line #527) into web-permission-sandbox-merge-master

Shared-surface conflicts resolve as unions: the fixture serves all four
projection keys (title/todos/permissions/goal) with both the /permission
and /goal command mirrors (the goal-fixture placeholder retires with
master), apps/cli carries both lines' dependency additions, and the README
Model Experience allowlist keeps both entries. The connection specs assert
the four-key baseline and the shifted approval/question replay indices;
the module graph regenerates over the merged dependency set.

packages/host/apiproxy/src/api/sessions.schema.ts

@@ -193,9 +193,13 @@ export const sessionPromptRequestSchema = z.object({
   content: z.array(contentBlockSchema),
 }) as unknown as z.ZodType<RequestPayload<'session.prompt'>>
 
-/** session.prompt response value. */
+/** session.prompt response value (the command slot appears only when the prompt dispatched a slash command). */
 export const sessionPromptValueSchema = z.object({
   accepted: z.literal(true),
+  command: z.object({
+    kind: z.literal('success'),
+    text: z.string().optional(),
+  }).optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'session.prompt'>>>
 
 /** session.cancel request payload. */