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.
920b350e57