fix(hosting): retry standard transient errors; type resolver scopes as list

- Treat TimeoutError and ConnectionError (including ConnectionResetError) as
  transient before the message and status checks. Bare instances have empty
  messages, so they were not retried.
- Type the ObservabilityTokenResolver scopes parameter as list[str], which is
  what the cache passes and what the README documents.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 5cbf5f6b-cc40-4b7e-a591-65848db73a12

Author: DheerajPannala

libraries/microsoft-agents-a365-observability-hosting/microsoft_agents_a365/observability/hosting/token_cache_helpers/agent_token_cache.py

@@ -21,7 +21,7 @@
 
 logger = logging.getLogger(__name__)
 
-ObservabilityTokenResolver = Callable[[str, str, Sequence[str]], str | Awaitable[str | None] | None]
+ObservabilityTokenResolver = Callable[[str, str, list[str]], str | Awaitable[str | None] | None]
 
 
 @dataclass
@@ -271,6 +271,9 @@ def _is_expired(self, entry: _Entry) -> bool:
         return True
 
     def _is_retriable_error(self, error: Exception) -> bool:
+        if isinstance(error, (TimeoutError, ConnectionError)):
+            return True
+
         message = str(error).lower()
         if "timeout" in message or "econnreset" in message or "network" in message:
             return True

tests/observability/hosting/token_cache_helpers/test_agent_token_cache.py

@@ -207,6 +207,22 @@ async def no_sleep(delay: float) -> None:
     assert await token_cache.get_observability_token("agent", "tenant") == token
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("error", [TimeoutError(), ConnectionResetError()])
+async def test_refresh_retries_standard_transient_exceptions(token_cache, monkeypatch, error):
+    """Bare timeout and connection-reset errors are retried even without a message."""
+    token = make_jwt(300)
+    resolver = MagicMock(side_effect=[error, token])
+
+    async def no_sleep(delay: float) -> None:
+        return None
+
+    monkeypatch.setattr(asyncio, "sleep", no_sleep)
+
+    assert await token_cache.refresh_observability_token("agent", "tenant", resolver) == token
+    assert resolver.call_count == 2
+
+
 @pytest.mark.asyncio
 async def test_refresh_deduplicates_concurrent_same_identity_acquisition(token_cache):
     """Concurrent refreshes for the same key share the first acquired token."""