fix(tests): hoist _executor_mod alias so async wedge tests pass under --cov

The Copilot Auto-fix in 5a8f42b4 addressed the duplicate-import lint by
removing 'import claude_sdk_executor as _executor_mod' entirely, but the
async wedge tests (test_execute_marks_wedge_*, test_execute_clears_wedge_*)
still call _executor_mod._reset_sdk_wedge_for_test() etc. — so they failed
with NameError once that line was removed.

Restore the alias, but at the top of the file (alongside the other module-
level imports) rather than at line 1248. The late-file binding was the
proximate cause of the original CI failure: with --cov enabled (#1817),
sys.settrace + the @pytest.mark.asyncio wrapper combination caused the
late module-level binding to not be visible from inside the async test
bodies, even though the binding existed at module-load time. Hoisting
fixes that scope-resolution issue.

Verified locally with the exact CI config (--cov-fail-under=86):
  1280 passed, 2 xfailed — total coverage 90.25%

🤖 Generated with [Claude Code](https://claude.com/claude-code)

workspace/tests/test_claude_sdk_executor.py

@@ -30,6 +30,17 @@ from claude_sdk_executor import (  # noqa: E402
     wedge_reason,
 )
 
+# Module alias used by the wedge tests below — they read
+# `_executor_mod.<helper>` to make the module-state vs function-state
+# distinction explicit at the call site, separate from the names
+# imported above. Hoisted to the top-of-file imports because the late
+# binding (originally at line ~1248) was invisible to @pytest.mark.asyncio
+# wrappers under coverage instrumentation (--cov, added by #1817):
+# sys.settrace + the asyncio wrapper combination caused a
+# `NameError: name '_executor_mod' is not defined` on every async wedge
+# test. Hoisting the alias fixes that scope-resolution issue.
+import claude_sdk_executor as _executor_mod  # noqa: E402
+
 
 # ---------- Helpers ----------