feat: canonical Nim client refactor with typed rows, pool, and allographer wrapper

- Extract wire protocol into clients/nim/src/baradb/wire.nim
- Add BaraError exception hierarchy
- Refactor BaraClient/SyncClient with typedRows, AsyncLock request queue, timeouts, TLS config
- Add BaraPool and optional HTTP fallback
- Add mock-server wire and pool unit tests
- Bump baradb nimble package to 1.2.0
- Make nim-allographer depend on canonical baradb client
- Use typed rows in allographer toJson
- Deprecate src/barabadb/client/client.nim
- Update docs/en/clients.md and clients/nim/README.md

clients/nim/tests/test_wire.nim

@@ -0,0 +1,68 @@
+import std/unittest
+import std/asyncdispatch
+import std/asyncnet
+import std/json
+import baradb/wire
+import baradb/client
+
+proc buildDataResponse(cols: seq[string], rows: seq[seq[WireValue]], affected: int): seq[byte] =
+  var payload: seq[byte] = @[]
+  payload.writeUint32(uint32(cols.len))
+  for c in cols:
+    payload.writeString(c)
+  for c in cols:
+    payload.add(byte(fkString))
+  payload.writeUint32(uint32(rows.len))
+  for row in rows:
+    for wv in row:
+      payload.serializeValue(wv)
+  result = buildMessage(mkData, 1'u32, payload)
+  var completePayload: seq[byte] = @[]
+  completePayload.writeUint32(uint32(affected))
+  result.add(buildMessage(mkComplete, 1'u32, completePayload))
+
+suite "Wire protocol":
+  test "buildMessage header is 12 bytes + payload":
+    let msg = buildMessage(mkQuery, 7'u32, toBytes("SELECT 1"))
+    check msg.len == 12 + 8
+
+  test "serialize/deserialize round-trip for WireValue":
+    let original = WireValue(kind: fkInt64, int64Val: 42)
+    var buf: seq[byte] = @[]
+    buf.serializeValue(original)
+    var pos = 0
+    let decoded = deserializeValue(buf, pos)
+    check decoded.kind == fkInt64
+    check decoded.int64Val == 42
+
+  test "client query against mock server returns typedRows and rows":
+    proc run() {.async.} =
+      var server = newAsyncSocket()
+      server.setSockOpt(OptReuseAddr, true)
+      server.bindAddr(Port(0), "127.0.0.1")
+      let port = server.getLocalAddr()[1]
+      server.listen()
+
+      proc serve() {.async.} =
+        let s = await server.accept()
+        let data = buildDataResponse(
+          @["name", "age"],
+          @[
+            @[WireValue(kind: fkString, strVal: "Alice"), WireValue(kind: fkInt32, int32Val: 30)],
+          ],
+          0,
+        )
+        await s.send(toString(data))
+        s.close()
+
+      asyncCheck serve()
+
+      let client = newClient(ClientConfig(host: "127.0.0.1", port: int(port), timeoutMs: 5000))
+      await client.connect()
+      let qr = await client.query("SELECT name, age FROM users")
+      check qr.rowCount == 1
+      check qr.typedRows[0][1].int32Val == 30
+      check qr.rows[0][1] == "30"
+      client.close()
+      server.close()
+    waitFor run()