Pin Pool initialize / acquire fork-guard arms

ISSUE-844 introduced fork-pid guards on Pool's lifecycle methods;
ISSUE-942 pinned the close() arm. The initialize() and acquire()
arms remained uncovered — a regression that drops either guard
would let a forked child silently share the parent's TCP fds with
corrupted reads / mixed request-response framing per ISSUE-843's
analysis.

Add coverage tests that monkeypatch _conn_mod._current_pid (no
real fork() needed; same pattern as ISSUE-1093 / ISSUE-966) and
assert each guard raises InterfaceError matching "after fork".

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

Author: antoineleclair

tests/test_pool_fork_guard_acquire_initialize.py

@@ -0,0 +1,42 @@
+"""Pin: ``ConnectionPool.initialize`` and
+``ConnectionPool.acquire`` raise ``InterfaceError`` when called
+after fork (creator pid != current pid).
+
+ISSUE-844 introduced these guards; ISSUE-942 pinned the close()
+fork branch only. The initialize / acquire arms were uncovered —
+a regression that drops either guard would let a forked child
+silently share the parent's TCP fds with corrupted reads / mixed
+request-response framing.
+
+Use the same monkeypatch pattern as ISSUE-1093 / ISSUE-966 — no
+real fork() needed.
+"""
+
+import os
+
+import pytest
+
+from dqliteclient import connection as _conn_mod
+from dqliteclient.exceptions import InterfaceError
+from dqliteclient.pool import ConnectionPool
+
+
+@pytest.mark.asyncio
+async def test_pool_initialize_raises_after_fork(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    pool = ConnectionPool(addresses=["h:9001"], min_size=1, max_size=2)
+    monkeypatch.setattr(_conn_mod, "_current_pid", os.getpid() + 1)
+    with pytest.raises(InterfaceError, match="after fork"):
+        await pool.initialize()
+
+
+@pytest.mark.asyncio
+async def test_pool_acquire_raises_after_fork(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    pool = ConnectionPool(addresses=["h:9001"], min_size=0, max_size=2)
+    monkeypatch.setattr(_conn_mod, "_current_pid", os.getpid() + 1)
+    with pytest.raises(InterfaceError, match="after fork"):
+        async with pool.acquire():
+            pytest.fail("should not reach")