Add Ollama ThinkOption runtime hints

[DragonFSKY]

Summary

• Register the custom Jackson serializer and deserializer used by Ollama ThinkOption for reflection hints.
• Add focused runtime hints coverage for the two ThinkOption Jackson handler classes.

Fixes #6043.

Testing

• ./mvnw -s <temp-empty-settings> -Dmaven.build.cache.enabled=false -pl models/spring-ai-ollama -am -Dtest=OllamaRuntimeHintsTests -Dsurefire.failIfNoSpecifiedTests=false test
• git diff --check

[DragonFSKY]

This is ready for review from my side.

I kept the change focused on the missing runtime hints for the ThinkOption Jackson serializer/deserializer and added targeted coverage in OllamaRuntimeHintsTests.

[sdeleuze]

Thanks, did you double check building a small native app to be sure? You not, could you?

[DragonFSKY]

Thanks for the reminder. I verified this with a small Spring Boot native application using the local PR branch artifacts.

Commands run:

• mvn -Pnative native:compile
• ./target/ollama-thinkoption-native-smoke

The native executable starts successfully and exercises both relevant paths:

• serializes an OllamaApi.ChatRequest built with .thinkHigh() to JSON containing "think":"high"
• deserializes "high" back to ThinkOption.ThinkLevel.HIGH

I also pushed a small follow-up adjustment after the local check.

Targeted tests were re-run:

./mvnw -pl models/spring-ai-ollama -am -Dtest=OllamaRuntimeHintsTests,ThinkOptionTests -Dsurefire.failIfNoSpecifiedTests=false test

Result: 32 tests passed.

Please let me know if you prefer any further changes.