feat(cmf): per-model generation defaults; safer delete-file default

- Each Local-models row gains default generation params — temperature, top-p,
  max tokens — applied by the gateway when the incoming request doesn't set
  them (an explicit request value always wins). Works for both the plain and
  streaming paths; top_p is now forwarded to OpenAI-compatible providers.
- The "also delete the model file from disk" checkbox in the delete dialog now
  defaults to UNCHECKED — deleting a pool entry no longer silently costs a
  multi-GB re-download/conversion.

src/config.rs

@@ -89,6 +89,14 @@ pub struct CmfServer {
     /// = force-enable on those layers.
     #[serde(default)]
     pub o1: String,
+    /// Default generation params for this model — applied by the gateway when
+    /// the incoming request does not set them (an explicit request value wins).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub temperature: Option<f32>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub top_p: Option<f32>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub max_tokens: Option<u32>,
 }
 
 /// CMF-format model factory: import a HuggingFace model, convert it to a
@@ -179,6 +187,9 @@ impl CmfCfg {
                 threads: self.threads,
                 gpu: self.gpu,
                 o1: String::new(),
+                temperature: None,
+                top_p: None,
+                max_tokens: None,
             }];
         }
         Vec::new()