Reorder xAI model descriptions in documentation (#320)

Author: mrubens

docs/providers/xai.md

@@ -8,6 +8,7 @@ keywords:
   - reasoning AI
   - vision models
   - large context
+  - Grok Code Fast
   - Grok-4
   - Grok-3
   - Grok-2
@@ -38,8 +39,8 @@ xAI is the company behind Grok, a large language model known for its conversatio
 Roo Code supports the following xAI Grok models:
 
 ### Current Models
-* `grok-4` (Default) - xAI's Grok-4 model with 256K context window, image support, and prompt caching
-* `grok-code-fast-1` - xAI's Grok Code Fast model with 262K context window, optimized for coding tasks
+* `grok-code-fast-1` (Default) - xAI's Grok Code Fast model with 262K context window and prompt caching, optimized for reasoning and coding tasks
+* `grok-4` - xAI's Grok-4 model with 262K context window, image support, and prompt caching
 * `grok-3` - xAI's Grok-3 model with 128K context window and prompt caching
 * `grok-3-fast` - xAI's Grok-3 fast model with 128K context window and prompt caching
 * `grok-3-mini` - xAI's Grok-3 mini model with 128K context window, reasoning support, and prompt caching
@@ -93,12 +94,12 @@ Choose `low` for simple queries that should complete quickly, and `high` for har
 
 ## Prompt Caching
 
-Prompt caching is available for select Grok models including `grok-4`, `grok-3`, `grok-3-fast`, `grok-3-mini`, and `grok-3-mini-fast`. This feature can reduce costs and improve response times.
+Prompt caching is available for select Grok models including `grok-code-fast-1`, `grok-4`, `grok-3`, `grok-3-fast`, `grok-3-mini`, and `grok-3-mini-fast`. This feature can reduce costs and improve response times.
 
 ---
 
 ## Pricing
 
 Pricing varies by model. Refer to the [xAI documentation](https://console.x.ai/) for current pricing information.
 
-**Note:** `grok-code-fast-1` is available for free through the [Roo Code Cloud provider](/providers/roo-code-cloud) during the promotional period. Standard pricing will apply when using the xAI provider directly in Roo Code.
+**Note:** `grok-code-fast-1` is available for free through the [Roo Code Cloud provider](/providers/roo-code-cloud) during the promotional period. Standard pricing will apply when using the xAI provider directly in Roo Code.