fix(adk): fix duplicate callback invocation for sub-agents

- Move ctxForSubAgents assignment before initAgentCallbacks to prevent
  callback handlers from being registered twice when sub-agents run
- Use filterOptions to ensure designated callbacks only fire for matching agents
- Update DeterministicTransfer GetType() to delegate to wrapped agent's type
- Add comprehensive tests for designated callback filtering

Change-Id: I03ee625e2d53fa8ed5f39afb33166f329f3ee34e

Author: shentongmartin