fix(mysql-session): commit writes when auto-commit is disabled

[Alexxigang]

Summary

• make MysqlSession write paths use consistent transactional behavior when connections start with autoCommit=false
• preserve the original connection auto-commit state instead of forcing it back to true
• add unit and H2 E2E regressions covering single-state writes, list append writes, and full-rewrite behavior

Why this fix

MysqlSession.save(...) previously committed the full-rewrite list path manually, but left append writes and other write paths relying on the connection's default auto-commit behavior. When a datasource returns connections with autoCommit=false, those writes can be lost. The previous full-rewrite path also mutated the connection state by always restoring autoCommit=true.

This change routes write operations through a shared transactional helper so the module commits its own writes consistently and only restores the connection state when it actually changed it.

Closes #1087.

Validation

• mvn -pl agentscope-extensions/agentscope-extensions-session-mysql -am -DskipTests test-compile
• mvn -pl agentscope-extensions/agentscope-extensions-session-mysql -am "-Dtest=MysqlSessionTest,MysqlSessionE2ETest" "-Dsurefire.failIfNoSpecifiedTests=false" test

[Alexxigang]

Friendly ping on this PR when maintainers have time. The fix and validation are ready on my side, and I'm happy to make any follow-up adjustments if review feedback comes in. Thanks!