Bug Description

The SignalAccountSchemaBase in zod-schema.providers-core.ts uses .strict() but is missing the accountUuid field. This field is:

1. Defined in the TypeScript type at types.signal.ts:10 as accountUuid?: string
2. Used at runtime for loop protection in signal/monitor/event-handler.ts:456
3. Wired in signal/monitor.ts:426
4. Tested in event-handler.inbound-contract.test.ts:176

Because the schema is .strict(), any user who sets channels.signal.accountUuid in their config will get a validation error, even though the field is valid and critical for preventing echo loops.

Steps to Reproduce

channels:
  signal:
    accountUuid: "a1b2c3d4-e5f6-7890-abcd-ef1234567890"

This config is rejected by validateConfigObject() with an unrecognized key error.

Expected Behavior

The config should be accepted, since accountUuid is a valid field used for loop protection.

Root Cause

Type/schema drift introduced in PR #31093 which added accountUuid to types and runtime but not to the Zod schema.