refactor(auth): remove vestigial Nous min_key_ttl/inference_auth_mode params

After the legacy session-key path was removed, two parameters became dead
surface on the Nous runtime-resolution chain:

- min_key_ttl_seconds: del'd inside refresh_nous_oauth_pure and pass-through /
  telemetry-only in refresh_nous_oauth_from_state, _try_import_shared_nous_state,
  _nous_device_code_login, and resolve_nous_runtime_credentials. It controlled the
  now-deleted agent-key mint TTL and drives no behavior.
- inference_auth_mode: with the legacy mode gone, AUTO and FRESH are behaviorally
  identical; the value only fed _normalize_nous_inference_auth_mode validation and
  oauth trace output, never a branch.

Removing inference_auth_mode orphaned its whole supporting cluster
(NOUS_INFERENCE_AUTH_MODE_AUTO/FRESH, NOUS_INFERENCE_AUTH_MODES,
_normalize_nous_inference_auth_mode), and dropping min_key_ttl_seconds orphaned
DEFAULT_AGENT_KEY_MIN_TTL_SECONDS — all deleted here.

Updated every caller (run_agent, auxiliary_client, credential_pool, proxy adapter,
runtime_provider, web_server, main, auth_commands, setup) and pruned the matching
test kwargs. Deleted two tests that exercised the removed surface
(test_legacy_auth_mode_is_rejected, test_try_refresh_..._accepts_explicit_auth_mode).

No behavior change: net -134 LOC of dead code.

hermes_cli/setup.py

@@ -781,7 +781,6 @@ def setup_model_provider(config: dict, *, quick: bool = False):
                         timeout=15.0,
                         insecure=False,
                         ca_bundle=None,
-                        min_key_ttl_seconds=5 * 60,
                     )
                 )
                 pool = load_pool(selected_provider)
@@ -2975,7 +2974,6 @@ def _run_portal_one_shot(config: dict) -> None:
             timeout=None,
             insecure=False,
             ca_bundle=None,
-            min_key_ttl_seconds=5 * 60,
         )
         try:
             auth_add_command(ns)