fix(redact): repr pass leaves already-masked values alone

The Python-repr pass ran after the MCP probe header scrub and collapsed
'Authorization': 'Digest ***' to '***', erasing the scheme word that scrub
deliberately keeps (tests/hermes_cli/test_mcp_probe_redaction.py went red
on rebase). Skip values that already carry a mask marker.

agent/redact.py

@@ -618,6 +618,11 @@ def _redact_python_repr_fields(text: str) -> str:
         # programmatic env lookups just like the ENV/JSON/YAML passes do.
         if _ENV_LOOKUP_VALUE_RE.match(value):
             return match.group(0)
+        # An upstream pass (MCP probe header scrub, _mask_token) already masked this
+        # value; re-masking would erase the scheme word it deliberately kept
+        # (``'Authorization': 'Digest ***'`` → ``'***'``).
+        if "***" in value or value.startswith("«redacted:"):
+            return match.group(0)
         # Do not retain head/tail characters here: escaped repr atoms can cross
         # a slicing boundary and leave an unescaped quote behind. A full mask is
         # parseable for both str and bytes values and leaks no opaque bytes.

tests/agent/test_redact.py

@@ -378,6 +378,12 @@ class TestPythonReprFields:
         text = "{'model': 'gpt-5', 'token_count': '123'}"
         assert redact_sensitive_text(text, force=True) == text
 
+    def test_already_masked_repr_value_keeps_its_scheme_word(self):
+        # An upstream scrub (MCP probe headers) leaves ``Digest ***``; the repr
+        # pass must not collapse that to a bare ``***`` and lose the scheme.
+        text = "headers={'Authorization': 'Digest ***'}"
+        assert redact_sensitive_text(text, force=True) == text
+
     def test_code_file_preserves_secret_shaped_fixture(self):
         text = "CONFIG = {'BRAVE_API_KEY': 'fixture-value-1234567890'}"
         assert redact_sensitive_text(text, force=True, code_file=True) == text