executeUpdate reads updateCount outside stateLock #197

Goal

executeUpdate returns updateCount without holding stateLock. Every write happens under the lock, but the read after execute has no happens-before edge, so a concurrent close() or execute can hand back a stale count.

Where

LibsqlStatement 146 to 149 and LibsqlPreparedStatement 97 to 104 read the field directly. getUpdateCount at 449 correctly locks.

Scope

• Add snapshotUpdateCount() that reads under stateLock.
• Use it in both executeUpdate methods.
• Do not add checkClosed(). Post-close executeUpdate keeps working, and the prepared statement already threw during execute.

Acceptance

• Both update paths read the count under the lock.
• ./mvnw -pl libsql-jdbc -am test green, including LibsqlStatementConcurrencyTest.
• A note in the PR records that this is a correctness fix, not a refactor, and that the race is hard to reproduce without instrumentation.