chore: exclude test fixtures from the sql-sop dogfooding pre-commit hook (#51)

The .pre-commit-config.yaml ran sql-sop with `--severity error` against
every `*.sql` file in the repo. The only SQL files currently in the
repo are the unit-test fixtures under tests/fixtures/ -- and those
fixtures deliberately contain bad SQL (E001 DELETE without WHERE, E002
DROP without IF EXISTS, E003 GRANT/REVOKE, E004 string concatenation in
WHERE, E005 INSERT without column list, E006 UPDATE without WHERE,
plus warning- and structural-rule fixtures) so the rule unit tests can
assert on those exact patterns.

Result: pre-commit.ci has been reporting "Found 6 issues (6 errors) in
1 file" against tests/fixtures/errors.sql on every single PR for
months. The pre-commit-ci status has been red the whole time but
hidden behind the also-always-red validate check (just fixed by #50);
on PRs that don't touch SQL fixtures, the dogfooding hook adds no
diagnostic value because the failures are by design.

Adding `exclude: ^tests/fixtures/` so the hook only runs against real
SQL files outside the fixtures tree. No real .sql files exist in the
repo today, so the hook is effectively dormant; the moment someone
adds a migration script or an example query outside tests/fixtures/
it kicks in. Verified locally that the exclude pattern matches all
four fixture files (clean.sql, contract_drift.sql, errors.sql,
warnings.sql).

Author: Pawansingh3889

.pre-commit-config.yaml

@@ -37,11 +37,16 @@ repos:
       - id: ruff-format
 
   # ── sql-sop dogfooding itself ─────────────────────────────────────
-  # Runs sql-sop on the project's own fixtures + any staged .sql files
-  # so a regression in a rule is caught before it ships.
+  # Runs sql-sop on staged .sql files so a regression in a rule is
+  # caught before it ships. Test fixtures under ``tests/fixtures/`` are
+  # excluded because those files deliberately contain bad SQL
+  # (E001..E006, S001..S003, etc.) to drive the rule unit tests --
+  # running the linter against them is guaranteed to fail and was
+  # turning pre-commit.ci red on every PR.
   - repo: https://github.com/Pawansingh3889/sql-guard
     rev: v0.7.0
     hooks:
       - id: sql-sop
         args: [--severity, error]
         files: \.sql$
+        exclude: ^tests/fixtures/