test(discord_tool): add regression test for per-token capability cache

Proves token A's detected capabilities do not leak to token B after the
fix in the preceding commit. Before the fix this test would have seen
both tokens return token A's cached value.

tests/tools/test_discord_tool.py

@@ -696,6 +696,38 @@ class TestCapabilityDetection:
         _detect_capabilities("tok", force=True)
         assert mock_req.call_count == 2
 
+    @patch("tools.discord_tool._discord_request")
+    def test_cache_is_keyed_by_token(self, mock_req):
+        """Regression: token A's capabilities must not leak to token B.
+
+        Before the fix, the cache was a single module-global dict. The first
+        call populated it and every subsequent call — regardless of token —
+        returned the same cached value, producing wrong schema gating for
+        rotated or multi-token deployments.
+        """
+        def _per_token_flags(method, path, token, **_kwargs):
+            # token A: both intents; token B: neither.
+            if token == "tok_a":
+                return {"flags": (1 << 14) | (1 << 18)}
+            return {"flags": 0}
+
+        mock_req.side_effect = _per_token_flags
+
+        caps_a = _detect_capabilities("tok_a")
+        caps_b = _detect_capabilities("tok_b")
+
+        assert caps_a["has_members_intent"] is True
+        assert caps_a["has_message_content"] is True
+        assert caps_b["has_members_intent"] is False
+        assert caps_b["has_message_content"] is False
+        # Each token should hit the endpoint exactly once.
+        assert mock_req.call_count == 2
+
+        # Re-requesting either token serves from its own cache entry.
+        _detect_capabilities("tok_a")
+        _detect_capabilities("tok_b")
+        assert mock_req.call_count == 2
+
 
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 # Config allowlist