feat: Add history config to live connections

[arnabnandy7]

Summary

Adds historyConfig support to LiveConnectConfig, enabling Java users to seed conversation history in Gemini 3.1 Live sessions.

Fixes #974.

Root cause

HistoryConfig was available on the wire-level LiveClientSetup, but it was not exposed through the public LiveConnectConfig accepted by AsyncLive.connect. Consequently, callers could not enable initial history processing.

Changes

• Expose historyConfig through LiveConnectConfig and its builder.
• Map the configuration to setup.historyConfig for both Gemini Developer API and Vertex AI.
• Add regression tests for both backend conversion paths.
• Update native-image reflection metadata.
• Document Gemini 3.1 Live history seeding in the README.

Validation

• mvn compile -DskipTests -Djacoco.skip=true
• Checkstyle passes with zero violations.
• Native-image reflection JSON files parse successfully.
• git diff --check passes.
• Tests compile successfully. Local execution is blocked by the existing Mockito configuration not supporting the installed JDK 26; use a repository-supported JDK such as JDK 21.