test(auth): align copilot-remove test with borrowed-credential policy (#31416)

PR #31416 (avoid persisting borrowed credential secrets) added
sanitize_borrowed_credential_payload, which strips access_token from
any auth.json pool entry whose (provider, source) isn't in the
_PERSISTABLE_PROVIDER_SOURCES allowlist.

(copilot, gh_cli) is borrowed (not in the allowlist), so the test
fixture's pre-seeded access_token now gets stripped at load_pool()
time, leaving the pool empty. resolve_target('1') then fails with
'No credential #1. Provider: copilot.'

Fix: align the test with the new contract. At runtime, copilot tokens
are hydrated by resolve_copilot_token() — mock that path so the pool
gets an entry the test can remove. The behavior under test
(suppression of gh_cli + env variants on remove) is unchanged.

CI repro on origin/main HEAD; reproduced locally with stock checkout.

tests/hermes_cli/test_auth_commands.py

@@ -1590,20 +1590,16 @@ def test_auth_remove_copilot_suppresses_all_variants(tmp_path, monkeypatch):
     hermes_home.mkdir(parents=True, exist_ok=True)
     monkeypatch.setenv("HERMES_HOME", str(hermes_home))
 
+    # The copilot pool entry is no longer persisted directly in auth.json —
+    # `(copilot, gh_cli)` is borrowed and stripped by
+    # sanitize_borrowed_credential_payload (PR #31416, May 2026). Tokens are
+    # hydrated at runtime via resolve_copilot_token(). Mock that path so the
+    # pool has an entry to remove.
     _write_auth_store(
         tmp_path,
         {
             "version": 1,
-            "credential_pool": {
-                "copilot": [{
-                    "id": "c1",
-                    "label": "gh auth token",
-                    "auth_type": "api_key",
-                    "priority": 0,
-                    "source": "gh_cli",
-                    "access_token": "ghp_fake",
-                }]
-            },
+            "credential_pool": {"copilot": []},
         },
     )
 
@@ -1611,7 +1607,14 @@ def test_auth_remove_copilot_suppresses_all_variants(tmp_path, monkeypatch):
     from hermes_cli.auth import is_source_suppressed
     from hermes_cli.auth_commands import auth_remove_command
 
-    auth_remove_command(SimpleNamespace(provider="copilot", target="1"))
+    with patch(
+        "hermes_cli.copilot_auth.resolve_copilot_token",
+        return_value=("ghp_fake", "gh"),
+    ), patch(
+        "hermes_cli.copilot_auth.get_copilot_api_token",
+        return_value="ghu_fake_api",
+    ):
+        auth_remove_command(SimpleNamespace(provider="copilot", target="1"))
 
     assert is_source_suppressed("copilot", "gh_cli")
     assert is_source_suppressed("copilot", "env:COPILOT_GITHUB_TOKEN")