fix(gui): admit todos in the history wire schema

sessionHistoryValueSchema declared only events/hasMore, so the fetch
carrier's Zod parse stripped the tail page's todos projection — the
in-process and fixture paths carried it while a real WebApiClient lost it.
The fetch-carrier spec pins the field through the wire round trip.

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

@@ -78,10 +78,17 @@ export const historyEntrySchema = z.object({
   view: toolEventViewSchema.optional(),
 }) satisfies z.ZodType<Wire<HistoryEntry>>
 
+/** One todo item of the tail page's session-level projection (the todo/write payload shape). */
+export const todoItemSchema = z.object({
+  content: z.string(),
+  status: z.union([z.literal('pending'), z.literal('in_progress'), z.literal('completed')]),
+})
+
 /** session.history response value. */
 export const sessionHistoryValueSchema = z.object({
   events: z.array(historyEntrySchema),
   hasMore: z.boolean(),
+  todos: z.array(todoItemSchema).optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'session.history'>>>
 
 /** ContentBlock passthrough: core is merge-extensible — the type discriminant envelope is strict, the rest stays wide. */