fix(slack): evict web_client cache on invalidation + clarify caching test (review)

Two review follow-ups on the web_client port:

- Gemini: `_invalidate_client` cleared only the async `_client_cache`, leaving
  stale/revoked synchronous `WebClient` instances in `_web_client_cache` on
  token revocation / auth-error eviction. Pop the token from both caches.
  New `test_invalidate_client_clears_web_client_cache` is load-bearing.

- github-code-quality: `assert adapter.web_client is adapter.web_client`
  tripped "comparison of identical values". The test is a genuine caching
  check (the property is invoked twice), but binding each access to a name
  makes that intent explicit and silences the false-positive.

https://claude.ai/code/session_01FyMxQn2BEAzmwKS1GZczKj

Author: claude

src/chat_sdk/adapters/slack/adapter.py

@@ -808,6 +808,7 @@ def _get_client(self, token: str | None = None) -> Any:
     def _invalidate_client(self, token: str) -> None:
         """Remove a cached client (e.g., on token revocation)."""
         self._client_cache.pop(token, None)
+        self._web_client_cache.pop(token, None)
 
     def _get_web_client_for_token(self, token: str) -> Any:
         """Return a synchronous ``slack_sdk.WebClient`` for *token*, cached.

tests/test_slack_web_client.py

@@ -109,7 +109,13 @@ def test_returns_same_instance_per_token(self):
         """Repeated access returns the exact same cached object (identity)."""
         adapter = _single_workspace_adapter()
 
-        assert adapter.web_client is adapter.web_client
+        # Bind each property access to a name so the identity check reads as a
+        # caching assertion (two calls → same object), not a tautological
+        # ``x is x`` self-comparison.
+        first = adapter.web_client
+        second = adapter.web_client
+
+        assert first is second
 
     def test_caches_under_the_resolved_token(self):
         """The cached client is keyed by the resolved token."""
@@ -119,6 +125,21 @@ def test_caches_under_the_resolved_token(self):
 
         assert adapter._web_client_cache["xoxb-cache-key"] is client
 
+    def test_invalidate_client_clears_web_client_cache(self):
+        """``_invalidate_client`` evicts the sync WebClient too (token revocation).
+
+        Load-bearing: without the ``_web_client_cache.pop`` in
+        ``_invalidate_client`` a revoked token's stale ``WebClient`` would
+        survive eviction and this assertion fails.
+        """
+        adapter = _single_workspace_adapter("xoxb-revoke")
+        client = adapter.web_client
+        assert adapter._web_client_cache["xoxb-revoke"] is client
+
+        adapter._invalidate_client("xoxb-revoke")
+
+        assert "xoxb-revoke" not in adapter._web_client_cache
+
 
 # ---------------------------------------------------------------------------
 # Deprecated ``client`` alias