Allow scheduled local-only Hermes services without chat handles

[mostlydev]

Motivation

Hermes validation currently requires Discord, Slack, or Telegram even when a service is invoked only by scheduler-owned direct jobs and has no delivery route. This forces a fake chat identity onto isolated background agents.

Constraints

• Preserve the handle requirement for interactive Hermes services.
• Permit zero handles only when at least one invocation exists and every invocation has an empty to target (local delivery).
• Keep token validation unchanged for configured handles.
• Add focused validation and jobs-generation tests.

Acceptance

A scheduled local-only Hermes service validates and materializes local-delivery jobs; an unscheduled handle-less service and any handle-less routed invocation still fail closed.