fix: strip non-SQL lines from alembic stdout before linting

Some repos emit JSON structured logs to stdout during env.py loading.
These get mixed into the alembic upgrade --sql output and cause squawk
syntax errors. Filter out lines starting with { or [ before passing
to squawk.

Author: stephen-kintsugi

squawk_alembic/hook.py

@@ -133,7 +133,18 @@ def generate_sql(filepath):
             f"squawk-alembic: alembic upgrade --sql failed for {filepath}:\n{result.stderr}"
         )
 
-    return result.stdout
+    return _strip_non_sql(result.stdout)
+
+
+def _strip_non_sql(output):
+    """Remove non-SQL lines (e.g. JSON logs) that env.py may emit to stdout."""
+    lines = []
+    for line in output.splitlines(keepends=True):
+        stripped = line.lstrip()
+        if stripped.startswith("{") or stripped.startswith("["):
+            continue
+        lines.append(line)
+    return "".join(lines)
 
 
 def validate_branch(branch):