Add DEFAULT_MAX_TOTAL_ROWS / DEFAULT_MAX_CONTINUATION_FRAMES constants

The literals 10_000_000 and 100_000 appeared verbatim as default
parameters across ~9 user-facing entry points in the client and
dbapi packages. Promote both to named constants on the wire layer
(the canonical home for governance bounds shared across packages)
so a future tuning change has one place to edit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitewire/__init__.py

@@ -41,6 +41,8 @@
 from dqlitewire.buffer import ReadBuffer, WriteBuffer
 from dqlitewire.codec import MessageDecoder, MessageEncoder, decode_message, encode_message
 from dqlitewire.constants import (
+    DEFAULT_MAX_CONTINUATION_FRAMES,
+    DEFAULT_MAX_TOTAL_ROWS,
     LEADER_ERROR_CODES,
     PROTOCOL_VERSION,
     PROTOCOL_VERSION_LEGACY,
@@ -80,6 +82,8 @@
 
 __all__ = [
     "ContinuationError",
+    "DEFAULT_MAX_CONTINUATION_FRAMES",
+    "DEFAULT_MAX_TOTAL_ROWS",
     "__version__",
     "DecodeError",
     "EncodeError",

src/dqlitewire/constants.py

@@ -155,3 +155,18 @@ def primary_sqlite_code(code: int) -> int:
 TX_AUTO_ROLLBACK_PRIMARY_CODES: frozenset[int] = frozenset(
     {SQLITE_ABORT, SQLITE_INTERRUPT, SQLITE_IOERR, SQLITE_CORRUPT, SQLITE_FULL}
 )
+
+
+# Cumulative-row cap for a single SELECT result spanning multiple
+# continuation frames. The default protects against unbounded memory
+# growth on a maliciously slow-drip server while staying well above
+# any realistic legitimate result set. Forwarded to every
+# :class:`DqliteConnection` the public ``connect()`` /
+# ``ConnectionPool`` / dbapi ``connect()`` entry points hand out.
+DEFAULT_MAX_TOTAL_ROWS = 10_000_000
+
+# Per-query continuation-frame cap. Complements
+# ``DEFAULT_MAX_TOTAL_ROWS``: a server sending one row per frame can
+# inflict O(n) Python decode work where n is the row cap; the frame
+# cap bounds that work even when the row cap is large.
+DEFAULT_MAX_CONTINUATION_FRAMES = 100_000