PRD 0062: supervisor override for egress token blocks

When the outbound DLP catches a token, route the block through the
existing supervisor approval queue instead of returning 403 outright.
The egress proxy holds the request open until the operator answers, then
remembers an approved value for the life of the proxy so the request --
and later ones carrying it -- flow through. Fails closed on rejection,
timeout, malformed response, or when supervise is disabled.

- ScanResult.matched carries the raw matched substring (sidecar-only;
  never logged or written to the proposal). scan_outbound and the token
  detectors take a safe_tokens set and skip approved values, continuing
  past a safelisted match so a second secret in the same request is
  still caught.
- New egress-token-allow proposal tool, written directly to the queue by
  the addon (the gitleaks-allow pattern from PRD 0061). build_token_allow
  _payload renders host/method/path/detector reason + redacted context.
- Async request hook polls the queue without stalling the proxy event
  loop; EGRESS_TOKEN_ALLOW_TIMEOUT_SECONDS (default 300) bounds the wait.
- Supervisor TUI renders egress-token-allow like gitleaks-allow: report
  only, modify unavailable, approval requires a recorded reason.
- Unit tests for the matched/safe-tokens plumbing, payload builder, tool
  constant round-trip, and TUI paths; README + PRD 0062.

Closes #261.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HnvBjPZC5V7qeQpFbQdDmS

tests/unit/test_dlp_detectors.py

@@ -445,5 +445,47 @@ class TestKnownSecretsNewVariants(unittest.TestCase):
         self.assertIsNotNone(result)
 
 
+class TestMatchedAndSafeTokens(unittest.TestCase):
+    """PRD 0062: detectors carry the raw matched value, and a safelisted
+    value is skipped so the supervisor can approve a specific token."""
+
+    def test_token_pattern_sets_matched(self):
+        token = "ghp_" + "A" * 36
+        result = scan_token_patterns(f"token: {token}")
+        assert result is not None
+        self.assertEqual(token, result.matched)
+
+    def test_safe_token_is_skipped(self):
+        token = "ghp_" + "A" * 36
+        self.assertIsNone(
+            scan_token_patterns(f"token: {token}", safe_tokens={token})
+        )
+
+    def test_safe_token_does_not_mask_other_token(self):
+        safe = "ghp_" + "A" * 36
+        other = "AKIAIOSFODNN7EXAMPLE"
+        result = scan_token_patterns(
+            f"a={safe} b={other}", safe_tokens={safe},
+        )
+        assert result is not None
+        self.assertEqual(other, result.matched)
+        self.assertIn("AWS", result.reason)
+
+    def test_known_secret_sets_matched_and_safelist_skips(self):
+        secret = "supersecretvalue123"
+        env = {"EGRESS_TOKEN_FOO": secret}
+        result = scan_known_secrets(f"x={secret}", env=env)
+        assert result is not None
+        self.assertEqual(secret, result.matched)
+        self.assertIsNone(
+            scan_known_secrets(f"x={secret}", env=env, safe_tokens={secret})
+        )
+
+    def test_crlf_block_has_no_matched_value(self):
+        result = scan_crlf_injection("path%0d%0aHost: evil")
+        assert result is not None
+        self.assertEqual("", result.matched)
+
+
 if __name__ == "__main__":
     unittest.main()