fix: Update background-only function description in AGENTS.md (#527)

Clarify background-only function requirements in documentation.

Signed-off-by: xuanyi-fu <[email protected]>

Author: xuanyi-fu

docs/public/AGENTS.md

@@ -30,7 +30,7 @@
 
 - **Dual-thread parallel rendering**: The main thread renders ReactLynx output immediately for the first screen, while the background thread constructs the full node tree and syncs state back to the main thread to avoid a white screen. (See [Rendering Process and Lifecycle](/react/lifecycle.md), [IFR](/guide/interaction/ifr.md))
 - **“Your code runs on two threads”**: Dual-thread React means your logic can run on both threads. However, not all code can execute in both environments—some APIs are only available on the background thread, and ReactLynx only executes events, lifecycle hooks, and `useEffect`-style side effects from the background thread.
-- **`'background only'`**: Any function that does not need to run on the main thread (for example event handlers, lifecycle hooks, side effects) or that touches background-only APIs must add `'background only'` as the first statement. Modules can declare `import "background-only"` to indicate they expect to run exclusively on the background thread.
+- **`'background only'`**: Any function **except a function component** that does not need to run on the main thread (for example event handlers, lifecycle hooks, side effects) or that touches background-only APIs must add `'background only'` as the first statement. Modules can declare `import "background-only"` to indicate they expect to run exclusively on the background thread.
 - **Main Thread Script (MTS)**: Functions marked with the `'main thread';` directive run directly on the main thread, ideal for high-frequency gestures, animations, and zero-delay feedback. Main-thread events must use the `main-thread:` prefix (for example `main-thread:bindtap`, `useMainThreadRef`). (See [Main Thread Script](/react/main-thread-script.md))
 - **Cross-thread communication**: Use `runOnMainThread` and `runOnBackground` for asynchronous cross-thread calls. Arguments must be JSON-serializable.