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.

run_agent.py

@@ -2999,22 +2999,15 @@ class AIAgent:
         self,
         *,
         force: bool = True,
-        inference_auth_mode: str | None = None,
     ) -> bool:
         if self.api_mode != "chat_completions" or self.provider != "nous":
             return False
 
         try:
-            from hermes_cli.auth import (
-                NOUS_INFERENCE_AUTH_MODE_AUTO,
-                resolve_nous_runtime_credentials,
-            )
+            from hermes_cli.auth import resolve_nous_runtime_credentials
 
-            selected_auth_mode = inference_auth_mode or NOUS_INFERENCE_AUTH_MODE_AUTO
             creds = resolve_nous_runtime_credentials(
-                min_key_ttl_seconds=max(60, int(os.getenv("HERMES_NOUS_MIN_KEY_TTL_SECONDS", "1800"))),
                 timeout_seconds=float(os.getenv("HERMES_NOUS_TIMEOUT_SECONDS", "15")),
-                inference_auth_mode=selected_auth_mode,
                 force_refresh=force,
             )
         except Exception as exc: