Document runtime provider parameters

docs/cli.md

@@ -33,6 +33,7 @@ Integration references:
 - `serve` requires an effective `prompt_dir` and `profile_dir` (from flags or config).
 - Positional arguments are rejected.
 - Prompt cache control is configured in prompt YAML (`messages[].cache_control`), not with CLI flags.
+- Provider-specific `reasoning_effort` and `extra_params` are configured in profile YAML or HTTP model overrides, not with CLI flags.
 
 ## Flag Reference
 
@@ -57,6 +58,11 @@ Integration references:
 - `--top-p <float>`: runtime top-p override.
 - `--timeout <duration>`: runtime timeout override (Go duration syntax, for example `30s`, `2m`).
 
+Numeric runtime override flags are presence-aware:
+
+- omitted numeric flags preserve the selected profile/default value
+- explicit zero values override the selected profile/default value (`--temperature 0`, `--max-tokens 0`, `--top-p 0`, `--timeout 0s`)
+
 ### `scriptorium render`
 
 - Supports the same flags as `run`, except: