feat: harden storage, schema persistence, fair benches, fix wire crash

Core storage: hash MemTable, WAL group commit, L0 compaction rebuild,
reader-writer lock, and a global StorageGate so HTTP workers and TCP
share the LSM safely under multi-thread access.

Schema: durable CREATE/ALTER/DROP under _schema:tables:* with full LSM
restore on open. Executor types/values/schema split into query/exec/.

Wire protocol: switch default MM to ARC — ORC cycle collector segfaulted
after ~20 async INSERTs. Fair multi-tier benchmarks (SQLite/HTTP/wire/PG)
and honesty docs for mixed-tier comparisons.

.gitignore

@@ -51,6 +51,18 @@ tests/nimforum_smoke_test
 
 benchmark_results.json
 pg_benchmark_results.json
+fair_benchmark_results.json
 benchmarks/bench_all
 benchmarks/compare
 .qwen/
+
+# Compiled test / module binaries
+tests/test_schema_persist
+tests/test_storage_hardening
+tests/test_wire_insert_stress
+src/barabadb/storage/lsm
+src/barabadb/storage/wal
+src/barabadb/storage/btree
+src/barabadb/storage/gate
+clients/nim/tests/test_pool
+clients/nim/tests/test_wire