fix: resolve current entry unlocked in try_refresh_matching no-hint branch

Follow-up to the #62614 salvage: try_refresh_matching (added by the
#69843 salvage after this PR's base) calls self.current() while already
holding the now-locking non-reentrant pool lock — a guaranteed deadlock
that git merges silently (no textual conflict). Use _current_unlocked()
and cover the method in the no-deadlock test.

agent/credential_pool.py

@@ -1907,7 +1907,7 @@ class CredentialPool:
                     None,
                 )
             else:
-                entry = self.current() or self._select_unlocked(refresh=False)
+                entry = self._current_unlocked() or self._select_unlocked(refresh=False)
             if entry is None:
                 return None
             self._current_id = entry.id

tests/agent/test_credential_pool.py

@@ -3619,6 +3619,11 @@ class TestCredentialPoolQueryLocking:
         assert pool.resolve_target("cred-1")[1] is not None
         # (env may seed extra singleton entries; just assert ours are present)
         assert {"cred-1", "cred-2"} <= {e.id for e in pool.entries()}
+        # try_refresh_matching's no-hint branch resolves the current entry
+        # while already holding the lock — must use _current_unlocked(), not
+        # current(), or it deadlocks on the non-reentrant lock (found when
+        # rebasing this fix over the #69843 salvage which added the method).
+        pool.try_refresh_matching()
 
     @pytest.mark.parametrize(
         "method,get_args",