docs: Fix rules description in AI overview (#48420)

Release Notes:

- N/A

docs/src/ai/overview.md

@@ -16,7 +16,7 @@ Zed integrates AI throughout the editor: agentic coding, inline transformations,
 
 - [Agent Panel](./agent-panel.md): Chat with AI agents that can read, write, and run code in your project.
 
-- [Rules](./rules.md): Define project-specific instructions for AI behavior.
+- [Rules](./rules.md): Define specific instructions for AI behavior.
 
 - [Tools](./tools.md): The built-in capabilities agents use: file operations, terminal commands, web search.
 

docs/src/ai/rules.md

@@ -1,6 +1,6 @@
 # Using Rules {#using-rules}
 
-Rules are prompts inserted at the beginning of each agent interaction. Add them via files in your worktree (`.rules`, etc.) or through the Rules Library for reuse across projects.
+Rules are prompts inserted at the beginning of each agent interaction. Add them via files in your worktree (`.rules`, etc.) or through the Rules Library for reuse across projects and threads.
 
 ## `.rules` files