refactor(sync): replace message reloads with incremental tail sync

shared/src/apiTypes.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { ListCodexSessionsRpcResponseSchema } from './apiTypes'
+import { ListCodexSessionsRpcResponseSchema, MessagesQuerySchema } from './apiTypes'
 
 describe('ListCodexSessionsRpcResponseSchema', () => {
     it('preserves Codex session messages when parsing runner RPC responses', () => {
@@ -29,3 +29,41 @@ describe('ListCodexSessionsRpcResponseSchema', () => {
         }
     })
 })
+
+describe('MessagesQuerySchema', () => {
+    it('parses a forward cursor with a bounded snapshot and epoch', () => {
+        expect(MessagesQuerySchema.parse({
+            afterAt: '1000',
+            afterSeq: '10',
+            untilAt: '2000',
+            untilSeq: '20',
+            epoch: '3',
+            limit: '200'
+        })).toEqual({
+            afterAt: 1000,
+            afterSeq: 10,
+            untilAt: 2000,
+            untilSeq: 20,
+            epoch: 3,
+            limit: 200
+        })
+    })
+
+    it('rejects mixed before and after directions', () => {
+        expect(MessagesQuerySchema.safeParse({
+            beforeAt: 1000,
+            beforeSeq: 10,
+            afterAt: 2000,
+            afterSeq: 20
+        }).success).toBe(false)
+    })
+
+    it('rejects an unpaired or unscoped until cursor', () => {
+        expect(MessagesQuerySchema.safeParse({ untilAt: 2000, untilSeq: 20 }).success).toBe(false)
+        expect(MessagesQuerySchema.safeParse({ afterAt: 1000, afterSeq: 10, untilAt: 2000 }).success).toBe(false)
+    })
+
+    it('rejects epoch without a forward cursor', () => {
+        expect(MessagesQuerySchema.safeParse({ epoch: 1 }).success).toBe(false)
+    })
+})