feat(oneshot): add --model / --provider / HERMES_INFERENCE_MODEL (#15704)

Makes hermes -z usable by sweeper without mutating user config.

- Top-level -m/--model and --provider flags that apply to -z/--oneshot
  (mirrors hermes chat's plumbing).
- HERMES_INFERENCE_MODEL env var as the parallel to HERMES_INFERENCE_PROVIDER
  for CI / scripted invocations.
- resolve_runtime_provider() gets the requested provider; when --model is
  given without --provider, detect_provider_for_model() auto-selects the
  provider that serves it (same semantic as /model in an interactive session).
- --provider without --model errors out with exit 2 — carrying a config
  model across to a different provider is usually wrong, and silently
  picking the provider's catalog default hides the mismatch.

Config defaults still used when both flags are omitted (existing behavior).

Validation (all live against OpenRouter):
  -z 'x' ....................... uses config default (opus-4.7)
  -z 'x' --model haiku-4.5 ..... haiku-4.5 via auto-detected openrouter
  -z 'x' --model ... --provider  pair as given
  HERMES_INFERENCE_MODEL=... -z  haiku-4.5 via env var
  -z 'x' --provider anthropic .. exits 2 with error to stderr

hermes_cli/main.py

@@ -6848,6 +6848,27 @@ For more help on a command:
             "auto-bypassed. Intended for scripts / pipes."
         ),
     )
+    # --model / --provider are accepted at the top level so they can pair
+    # with -z without needing the `chat` subcommand.  If neither -z nor a
+    # subcommand consumes them, they fall through harmlessly as None.
+    # Mirrors `hermes chat --model ... --provider ...` semantics.
+    parser.add_argument(
+        "-m",
+        "--model",
+        default=None,
+        help=(
+            "Model override for this invocation (e.g. anthropic/claude-sonnet-4.6). "
+            "Applies to -z/--oneshot. Also settable via HERMES_INFERENCE_MODEL env var."
+        ),
+    )
+    parser.add_argument(
+        "--provider",
+        default=None,
+        help=(
+            "Provider override for this invocation (e.g. openrouter, anthropic). "
+            "Applies to -z/--oneshot. Also settable via HERMES_INFERENCE_PROVIDER env var."
+        ),
+    )
     parser.add_argument(
         "--resume",
         "-r",
@@ -9133,7 +9154,11 @@ Examples:
     if getattr(args, "oneshot", None):
         from hermes_cli.oneshot import run_oneshot
 
-        sys.exit(run_oneshot(args.oneshot))
+        sys.exit(run_oneshot(
+            args.oneshot,
+            model=getattr(args, "model", None),
+            provider=getattr(args, "provider", None),
+        ))
 
     # Handle top-level --resume / --continue as shortcut to chat
     if (args.resume or args.continue_last) and args.command is None: