…uator (#29344)

Eleven new tests pinning the #29344 fix.  Layout mirrors the existing
"Fix D" entitlement section so the bad-credentials disambiguator
sits alongside the entitlement-block tests it complements.

Classifier-level coverage:

* ``test_is_entitlement_failure_false_for_bad_credentials_wke_suffix``
  — verbatim shape from the reporter's wire capture
  (``{code: 'caller does not have permission', error: 'OAuth2 access
  token could not be validated. [WKE=unauthenticated:bad-credentials]'}``)
  ↦ classifier must return False so the refresh path runs.
* ``test_is_entitlement_failure_false_for_wke_suffix_in_normalized_shape``
  — same body after ``_extract_api_error_context`` has rewritten it
  to ``{reason, message}``.  The disambiguator must fire in BOTH
  shapes; without this guard the production call site at
  ``_recover_with_credential_pool`` (which goes through the
  normalised extractor) would still misclassify.
* ``test_is_entitlement_failure_false_for_any_wke_unauthenticated_variant``
  — parametrised forward-compat: ``bad-credentials``,
  ``expired-token``, ``revoked``, ``some-future-reason``.  xAI
  documents the prefix as stable, the suffix after the colon as a
  reason code that can grow; every variant under
  ``unauthenticated:`` must route to refresh.
* ``test_is_entitlement_failure_false_via_oauth2_validation_phrase_alone``
  — belt-and-braces guard: if a future API revision drops the WKE
  suffix but keeps "OAuth2 access token could not be validated", we
  still classify correctly.
* ``test_is_entitlement_failure_wke_signal_overrides_entitlement_keywords``
  — defensive: if a body ever carries BOTH the WKE suffix and
  entitlement language, the WKE signal wins.  Auth is recoverable;
  entitlement isn't, and a refreshed token will resurface the
  entitlement message on the next request.
* ``test_is_entitlement_failure_case_insensitive_wke_match`` —
  pins that the classifier lowercases the haystack so a future xAI
  build that uppercases the prefix doesn't reintroduce the bug.

Recovery-path coverage (end-to-end through
``_recover_with_credential_pool``):

* ``test_recover_with_credential_pool_refreshes_on_xai_bad_credentials_403``
  — the headline test the reporter requested: a bad-credentials 403
  with the exact wire body must call ``try_refresh_current()``
  exactly once and ``_swap_credential`` once.  Pre-fix this returned
  ``(False, _)`` because the entitlement classifier over-matched and
  short-circuited the refresh path.
* ``test_recover_with_credential_pool_still_blocks_real_entitlement``
  — companion regression guard for #26847: a pure unsubscribed-
  account body (no WKE suffix, no OAuth2-validation phrase) must
  still surface as entitlement and skip refresh.  The new
  disambiguator must not weaken the original loop-protection it
  was added to preserve.

The scaffolding reuses ``_make_codex_agent``, ``_FakePool``, and the
existing ``MagicMock`` patterns from the surrounding tests so the
new section reads as a natural extension of "Fix D" rather than a
separate test file.

…29344)

_recover_with_credential_pool had a second classification site that blanket-
treated any 403 against xai-oauth as entitlement (defense-in-depth for
#26847).  That override defeated the new _is_entitlement_failure
disambiguator from the parent commit — bad-credentials 403s still
short-circuited the refresh path.

Apply the same WKE-unauthenticated / OAuth2-validation-phrase guard at
the override site so xAI's authoritative 'this is auth, not entitlement'
signal wins there too.  The #26847 catch-all still triggers for genuine
entitlement bodies that don't carry the disambiguator.

Closes the end-to-end gap exposed by
test_recover_with_credential_pool_refreshes_on_xai_bad_credentials_403.