Prevent pre-push contract drift (#3113)

Add a lightweight regression for the documented local pre-push build gate so the skip hatch and lockfile-grade cargo build command stay aligned with operator docs.

Constraint: Issue #696 scope is limited to pre-push hook contract drift after ROADMAP #694.\nRejected: Reworking the hook harness or roadmap board | unnecessary for the focused drift guard.\nConfidence: high\nScope-risk: narrow\nDirective: Keep the hook docs, skip hatch, and cargo --locked command in sync when changing local push gates.\nTested: bash -n .github/hooks/pre-push; python3 tests/test_pre_push_hook_contract.py -v; git diff --check\nNot-tested: Full cargo workspace build; Rust code was not touched.

docs/g013-roadmap-pinpoints-693-695-verification-map.md

@@ -19,6 +19,8 @@ covered by the Claw Code 2.0 board.
 - Install command: `git config core.hooksPath .github/hooks`
 - Gate: `cargo build --manifest-path rust/Cargo.toml --workspace --locked`
 - Escape hatch: `SKIP_CLAW_PRE_PUSH_BUILD=1` prints an explicit skip message.
+- Regression test: `tests/test_pre_push_hook_contract.py` locks the skip
+  hatch and `--locked` build command contract.
 - Purpose: mirror the CI build job locally so stale field/variant references are
   caught before push.
 
@@ -41,6 +43,7 @@ python3 scripts/generate_cc2_board.py
 python3 scripts/validate_cc2_board.py --board .omx/cc2/board.json
 python3 .omx/cc2/validate_issue_parity_intake.py .omx/cc2/issue-parity-intake.json
 bash -n .github/hooks/pre-push
+python3 tests/test_pre_push_hook_contract.py -v
 cargo fmt --manifest-path rust/Cargo.toml --all -- --check
 cargo test --manifest-path rust/Cargo.toml -p claw-analog rag_response_ -- --nocapture
 cargo test --manifest-path rust/Cargo.toml -p runtime startup_preflight -- --nocapture

tests/test_pre_push_hook_contract.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+import os
+import subprocess
+import unittest
+from pathlib import Path
+
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+PRE_PUSH_HOOK = REPO_ROOT / '.github' / 'hooks' / 'pre-push'
+
+
+class PrePushHookContractTests(unittest.TestCase):
+    def test_skip_escape_hatch_exits_successfully_with_stderr_notice(self) -> None:
+        env = os.environ.copy()
+        env['SKIP_CLAW_PRE_PUSH_BUILD'] = '1'
+
+        result = subprocess.run(
+            ['bash', str(PRE_PUSH_HOOK)],
+            cwd=REPO_ROOT,
+            env=env,
+            check=True,
+            capture_output=True,
+            text=True,
+        )
+
+        self.assertEqual('', result.stdout)
+        self.assertIn('SKIP_CLAW_PRE_PUSH_BUILD=1', result.stderr)
+        self.assertIn('skipping cargo workspace build', result.stderr)
+
+    def test_default_build_gate_uses_workspace_locked_cargo_build(self) -> None:
+        hook = PRE_PUSH_HOOK.read_text()
+
+        self.assertIn(
+            'cargo build --manifest-path rust/Cargo.toml --workspace --locked',
+            hook,
+        )
+        self.assertIn(
+            'build_cmd=(cargo build --manifest-path rust/Cargo.toml --workspace --locked)',
+            hook,
+        )
+
+
+if __name__ == '__main__':
+    unittest.main()