Add Python parity features to veadk-java

[sunnyji-coder]

Summary

• Add VeADK Java parity features based on the latest Python implementation: Agent facade, typed config loading, run processors, metadata, memory/knowledgebase facades, and Ark embedding support.
• Expand Ark LLM behavior: fallback models, generation config mapping, structured JSON schema output, multimodal image/video inputs, tool-call history round trip, streaming parallel tool-call assembly, finishReason and usage metadata.
• Add Python-aligned session persistence behavior with compatibility-preserving legacy callback semantics, plus optional SQLite short-term memory storage with stale-view/concurrent append protection.
• Add parity documentation and public API compatibility/regression tests.

Tests

• ./mvnw -o -B -ntp clean verify
• 130 tests passed across core and SQLite memory modules
• Reactor build, Spotless, JaCoCo reports, example compile, JAR/source/Javadoc packaging passed

Compatibility notes

• Existing Java constructors and legacy zero-argument SaveSessionToMemoryCallback behavior are preserved.
• SQLite support is introduced as an optional module so the core artifact does not transitively require sqlite-jdbc.