Add benchmark script and expand test coverage to 105 tests

Publish benchmark.mjs for reproducibility. Add autocommit
fairness note to benchmark output.

Expand tests: sync methods, batch execution, prepared statement
sync, transaction sync, named parameters, extended type conversions
(BigInt, Date, undefined, unicode, Object/Array as JSON), persistence
across restart, database open variations, and edge cases.

Author: semihalev

.gitignore

@@ -11,8 +11,7 @@ node_modules/
 npm/*/README.md
 npm/*/package.json
 
-# Benchmarks (devDependency on better-sqlite3)
-benchmark.mjs
+# Profiling scripts
 profile.mjs
 
 # OS