feat(security): deny writes to startup and global git config

Block write tool edits to secondary shell startup files and global git config paths while preserving project-local `.git/config` writes.

agent/file_safety.py

@@ -51,6 +51,10 @@ def build_write_denied_paths(home: str) -> set[str]:
             os.path.join(home, ".profile"),
             os.path.join(home, ".bash_profile"),
             os.path.join(home, ".zprofile"),
+            os.path.join(home, ".zshenv"),
+            os.path.join(home, ".zlogin"),
+            os.path.join(home, ".bash_login"),
+            os.path.join(home, ".gitconfig"),
             os.path.join(home, ".netrc"),
             os.path.join(home, ".pgpass"),
             os.path.join(home, ".npmrc"),
@@ -78,6 +82,7 @@ def build_write_denied_prefixes(home: str) -> list[str]:
             os.path.join(home, ".azure"),
             os.path.join(home, ".config", "gh"),
             os.path.join(home, ".config", "gcloud"),
+            os.path.join(home, ".config", "git"),
         ]
     ]
 

tests/tools/test_write_deny.py

@@ -69,9 +69,24 @@ class TestWriteDenyExactPaths:
 
     def test_shell_profiles(self):
         home = str(Path.home())
-        for name in [".bashrc", ".zshrc", ".profile", ".bash_profile", ".zprofile"]:
+        for name in [
+            ".bashrc", ".zshrc", ".profile", ".bash_profile", ".zprofile",
+            ".zshenv", ".zlogin", ".bash_login",
+        ]:
             assert _is_write_denied(os.path.join(home, name)) is True, f"{name} should be denied"
 
+    def test_global_git_config_paths(self):
+        home = str(Path.home())
+        for path in [
+            os.path.join(home, ".gitconfig"),
+            os.path.join(home, ".config", "git", "config"),
+            os.path.join(home, ".config", "git", "hooks", "pre-commit"),
+        ]:
+            assert _is_write_denied(path) is True, f"{path} should be denied"
+
+    def test_project_git_config_allowed(self):
+        assert _is_write_denied("/tmp/someproject/.git/config") is False
+
     def test_package_manager_configs(self):
         home = str(Path.home())
         for name in [".npmrc", ".pypirc", ".pgpass"]:

tools/skills_guard.py

@@ -252,7 +252,7 @@ THREAT_PATTERNS = [
     (r'\bcrontab\b',
      "persistence_cron", "medium", "persistence",
      "modifies cron jobs"),
-    (r'\.(bashrc|zshrc|profile|bash_profile|bash_login|zprofile|zlogin)\b',
+    (r'\.(bashrc|zshrc|zshenv|profile|bash_profile|bash_login|zprofile|zlogin)\b',
      "shell_rc_mod", "medium", "persistence",
      "references shell startup file"),
     (r'authorized_keys',