Update index.mdx to use correct idle/warm/cold terminology

Remove "hibernate" and "30 seconds" references in favor of
accurate warm/cold state descriptions.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: kcmartin

src/content/docs/index.mdx

@@ -41,18 +41,18 @@ Sprites are ideal for:
 - **AI Code Execution** - Running code generated by language models (like Claude Code) in isolated, secure environments
 - **Untrusted Code** - Isolating and executing user-submitted code safely without risking the rest of your system
 - **Development Environments** - Building persistent development environments that maintain state between sessions
-- **Long-lived Services** - Hosting services that hibernate automatically and resume on request
+- **Long-lived Services** - Hosting services that go idle automatically and resume on request
 - **CI/CD Tasks** - Testing code against live git repositories with full environment access
 
 ## Core Concepts
 
 ### Persistence
 
-Every Sprite has a persistent, standard ext4 filesystem. During execution, data is written to fast NVMe storage. When the Sprite hibernates, that data is backed up to durable object storage and automatically restored when it wakes up.
+Every Sprite has a persistent, standard ext4 filesystem. During execution, data is written to fast NVMe storage. When the Sprite goes idle, that data is backed up to durable object storage and automatically restored when it wakes up.
 
-### Automatic Hibernation
+### Automatic Idle Behavior
 
-Sprites automatically hibernate after a period of inactivity (30 seconds by default). While hibernated, there are no compute charges and your full filesystem is preserved. The Sprite wakes instantly on the next request.
+Sprites become `warm` immediately when idle, and may eventually go `cold`. While idle, there are no compute charges and your full filesystem is preserved. The Sprite wakes on the next request—`warm` Sprites resume quickly, `cold` Sprites take a bit longer.
 
 ### HTTP Access