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_supervise.py

@@ -322,11 +322,22 @@ class TestToolConstants(unittest.TestCase):
                 TOOL_CAPABILITY_BLOCK,
                 supervise.TOOL_EGRESS_BLOCK,
                 TOOL_GITLEAKS_ALLOW,
+                supervise.TOOL_EGRESS_TOKEN_ALLOW,
                 supervise.TOOL_LIST_EGRESS_ROUTES,
             ),
             supervise.TOOLS,
         )
 
+    def test_token_allow_proposal_roundtrips(self):
+        p = Proposal.new(
+            bottle_slug="dev",
+            tool=supervise.TOOL_EGRESS_TOKEN_ALLOW,
+            proposed_file="host: api.example.com\n",
+            justification="false positive",
+            current_file_hash="h",
+        )
+        self.assertEqual(p, Proposal.from_dict(p.to_dict()))
+
     def test_component_map_has_egress_entries(self):
         self.assertEqual(
             {