feat: add grok-code-fast-1 support for xAI provider (#4472)

Signed-off-by: HikaruEgashira <hikaru-egashira@c-fo.com>

crates/goose/src/model.rs

@@ -58,10 +58,12 @@ static MODEL_SPECIFIC_LIMITS: Lazy<Vec<(&'static str, usize)>> = Lazy::new(|| {
         ("qwen2-70b", 262_144),
         ("qwen2", 128_000),
         ("qwen3-32b", 131_072),
+        // xai
+        ("grok-4", 256_000),
+        ("grok-code-fast-1", 256_000),
+        ("grok", 131_072),
         // other
         ("kimi-k2", 131_072),
-        ("grok-4", 256_000),
-        ("grok", 131_072),
     ]
 });
 

crates/goose/src/providers/xai.rs

@@ -13,8 +13,9 @@ use rmcp::model::Tool;
 use serde_json::Value;
 
 pub const XAI_API_HOST: &str = "https://api.x.ai/v1";
-pub const XAI_DEFAULT_MODEL: &str = "grok-3";
+pub const XAI_DEFAULT_MODEL: &str = "grok-code-fast-1";
 pub const XAI_KNOWN_MODELS: &[&str] = &[
+    "grok-code-fast-1",
     "grok-4-0709",
     "grok-3",
     "grok-3-fast",