refactor(config): dedupe install and typing schema definitions

src/config/zod-schema.session.ts

@@ -8,6 +8,7 @@ import {
   InboundDebounceSchema,
   NativeCommandsSettingSchema,
   QueueSchema,
+  TypingModeSchema,
   TtsConfigSchema,
 } from "./zod-schema.core.js";
 import { sensitive } from "./zod-schema.sensitive.js";
@@ -50,14 +51,7 @@ export const SessionSchema = z
     resetByChannel: z.record(z.string(), SessionResetConfigSchema).optional(),
     store: z.string().optional(),
     typingIntervalSeconds: z.number().int().positive().optional(),
-    typingMode: z
-      .union([
-        z.literal("never"),
-        z.literal("instant"),
-        z.literal("thinking"),
-        z.literal("message"),
-      ])
-      .optional(),
+    typingMode: TypingModeSchema.optional(),
     mainKey: z.string().optional(),
     sendPolicy: SessionSendPolicySchema.optional(),
     agentToAgent: z