fix(xai): drop models being retired May 15, 2026 from pickers (#23291)

xAI is retiring grok-4, grok-4-0709, grok-4-fast{,-reasoning,-non-reasoning},
grok-4-1-fast{,-reasoning,-non-reasoning}, and grok-code-fast-1 on
May 15, 2026 at 12:00 PT. Remove them from the static fallbacks so the
`hermes model` picker, gateway /model picker, and setup wizard stop
auto-suggesting models that will be dead in days.

- _XAI_STATIC_FALLBACK in hermes_cli/models.py now lists only grok-4.20-*
  and grok-4.3 (the live replacements).
- copilot lists in hermes_cli/models.py and hermes_cli/setup.py drop
  grok-code-fast-1 (Copilot proxies it through xAI, so the upstream
  retirement breaks it there too).

Old configs that already reference retired IDs keep working until xAI
flips the switch — context-length lookups in agent/model_metadata.py and
the cache-affinity-header logic in provider_profiles still recognise the
old names. The cleanup here is purely about not advertising them to new
users.

Closes #23278.

Source: https://docs.x.ai/developers/migration/may-15-retirement

hermes_cli/setup.py

@@ -89,7 +89,6 @@ _DEFAULT_PROVIDER_MODELS = {
         "claude-sonnet-4.5",
         "claude-haiku-4.5",
         "gemini-2.5-pro",
-        "grok-code-fast-1",
     ],
     "gemini": [
         "gemini-3.1-pro-preview", "gemini-3-pro-preview",