[skip-runtime-e2e] examples: add planning and connectors examples

[Drifter-yh]

Summary

• add a minimal planning example using generatePlan() and executePlan()
• add a read-only connectors example using listConnectors()
• follow the existing Java example layout and Maven setup

Testing

• both example projects compile successfully
• full Maven verify passes locally
• live execution was not run because no local AxonFlow community stack was available; the planning example also requires an LLM provider as documented in the source

Skip-runtime-e2e justification

This PR only adds the two example directories requested in #146. The issue explicitly scopes integration.yml wiring as optional because the planning example requires an LLM provider that may not be available in CI. No SDK runtime behavior is changed.
Closes #146