fix(tools): flatten nested anyOf schemas for Vertex AI compatibility

Claude API on Vertex AI (Cloud Code Assist) rejects nested anyOf schemas
as invalid JSON Schema draft 2020-12. This change:

- Add tryFlattenLiteralAnyOf() to convert Type.Union([Type.Literal(...)])
  patterns from anyOf with const values to flat enum arrays
- Update stringEnum helper in bash-tools to use Type.Unsafe with flat enum
- Flatten BrowserActSchema from discriminated union to single object
- Simplify TelegramToolSchema to use Type.String() for IDs

Fixes 400 errors when sending messages through WhatsApp/Telegram providers.

src/agents/bash-tools.ts

@@ -39,17 +39,19 @@ const DEFAULT_PATH =
   process.env.PATH ??
   "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin";
 
-const stringEnum = (
-  values: readonly string[],
-  options?: Parameters<typeof Type.Union>[1],
+// NOTE: Using Type.Unsafe with enum instead of Type.Union([Type.Literal(...)])
+// because Claude API on Vertex AI rejects nested anyOf schemas as invalid JSON Schema.
+// Type.Union of literals compiles to { anyOf: [{enum:["a"]}, {enum:["b"]}, ...] }
+// which is valid but not accepted. A flat enum { type: "string", enum: [...] } works.
+const stringEnum = <T extends readonly string[]>(
+  values: T,
+  options?: { description?: string },
 ) =>
-  Type.Union(
-    values.map((value) => Type.Literal(value)) as [
-      ReturnType<typeof Type.Literal>,
-      ...ReturnType<typeof Type.Literal>[],
-    ],
-    options,
-  );
+  Type.Unsafe<T[number]>({
+    type: "string",
+    enum: values as unknown as string[],
+    ...options,
+  });
 
 export type BashToolDefaults = {
   backgroundMs?: number;