[Feature] wake API: support agentId parameter to target specific agents

Summary

The wake Gateway API currently only sends wake events to the caller's main session. It would be useful to specify a target agentId to wake a specific agent.

Current Behavior

openclaw gateway call wake --params '{"text":"message","mode":"now","agentId":"claudebot1"}'
# Error: invalid wake params: unexpected property 'agentId'

Proposed Behavior

# Wake a specific agent
openclaw gateway call wake \
  --params '{"text":"message","mode":"now","agentId":"claudebot1"}'

# Wake default (current) agent (backward compatible)
openclaw gateway call wake \
  --params '{"text":"message","mode":"now"}'

Use Case

Multi-agent setups where a script or automation needs to send a message to a specific agent and have it process immediately. Currently the only workaround is using cron add with --agent, but:

1. --at type jobs have a bug (state.nextRunAtMs not initialized)
2. Creates persistent jobs that need cleanup

A direct wake with agentId would be cleaner and more reliable.

Environment

• OpenClaw 2026.1.30
• Multi-agent setup with separate workspaces