Week 4: Production Hardening — Thread Safety, Fuzz Tests, Property-Based Tests, NimForum Smoke Test

Thread Safety:
- Add lock to BTreeIndex (insert/get/scan/remove/contains)
- Add lock to InvertedIndex (addDocument/removeDocument/search/bm25/tfidf/fuzzy/regex)
- Add ctxLock to ExecutionContext for DDL/schema metadata, autoIncCounters, sequences
- Deep-copy sessionVars in cloneForConnection() to isolate per-connection state
- Fix activeConnections check-then-act race with Lock

Wire Protocol Hardening:
- Fix RangeDefect in deserializeValue for invalid FieldKind bytes
- Fix IndexDefect in fkFloat32/fkFloat64 by reusing readUint32/readUint64
- Fix int32/int64 cast from uint32/uint64 to use cast[] instead of constructor
- Fix parseHeader to validate MsgKind instead of holey enum cast

Property-Based Tests (tests/prop_test.nim):
- 8 invariants for evalExprValue: literal types, commutativity, identity,
  double negation, NULL propagation

Wire Protocol Fuzz (tests/fuzz_test.nim):
- 7 fuzz tests: random bytes deserialization, truncated buffers,
  MsgKind casts, parseHeader logic, message roundtrips

NimForum Adapter Smoke Test (tests/nimforum_smoke_test.nim):
- Full TCP server lifecycle with adapter CRUD and parameterized queries

Test Results: 423 tests pass, 0 failures

tests/nimforum_smoke_test.nim

@@ -0,0 +1,69 @@
+## NimForum Adapter Smoke Test
+import std/unittest
+import std/osproc
+import std/os
+import std/strutils
+import std/strtabs
+import std/times
+
+import ../adaptors/nim/baradb_sqlite as sqlite
+
+suite "NimForum Adapter Smoke Test":
+  var serverProcess: Process
+  var port: int
+  var dataDir: string
+
+  setup:
+    port = 35000 + (getTime().toUnix.int mod 10000)
+    dataDir = getTempDir() / "baradb_nimforum_" & $port
+    createDir(dataDir)
+    var env = newStringTable()
+    for key, val in envPairs():
+      env[key] = val
+    env["BARADB_PORT"] = $port
+    env["BARADB_DATA_DIR"] = dataDir
+    env["BARADB_LOG_LEVEL"] = "error"
+    serverProcess = startProcess("./build/baradadb", env=env, options={poStdErrToStdOut, poDaemon})
+    sleep(800)
+
+  teardown:
+    if serverProcess != nil:
+      serverProcess.terminate()
+      discard serverProcess.waitForExit()
+    removeDir(dataDir)
+
+  test "Adapter basic CRUD over TCP":
+    var db = open("127.0.0.1:" & $port, "", "", "default")
+
+    db.exec(sql"CREATE TABLE nf_test (id INT PRIMARY KEY, name STRING)")
+    db.exec(sql"INSERT INTO nf_test (id, name) VALUES (1, 'hello')")
+    db.exec(sql"INSERT INTO nf_test (id, name) VALUES (2, 'world')")
+
+    let rows = db.getAllRows(sql"SELECT * FROM nf_test")
+    check rows.len == 2
+
+    let row = db.getRow(sql"SELECT * FROM nf_test WHERE id = 1")
+    check row.len == 2
+    check row[0] == "1"
+    check row[1] == "hello"
+
+    let val = db.getValue(sql"SELECT name FROM nf_test WHERE id = 2")
+    check val == "world"
+
+    let cnt = db.getValue(sql"SELECT count(*) FROM nf_test")
+    check cnt == "2"
+
+    db.close()
+
+  test "Adapter parameterized queries":
+    var db = open("127.0.0.1:" & $port, "", "", "default")
+
+    db.exec(sql"CREATE TABLE nf_params (id INT PRIMARY KEY, val STRING)")
+    db.exec(sql"INSERT INTO nf_params (id, val) VALUES (?, ?)", 10, "ten")
+    db.exec(sql"INSERT INTO nf_params (id, val) VALUES (?, ?)", 20, "twenty")
+
+    let row = db.getRow(sql"SELECT val FROM nf_params WHERE id = ?", 10)
+    check row.len >= 1
+    check row[row.len - 1] == "ten"
+
+    db.close()