Refine early return guard clause in error handling

Update error handling guard clause to include time check.

The simpler "!enabled || strip.isUpdating()" pattern regularly causes usermods to stop responding when many LEDs are driven.

Author: softhack007

AGENTS.md

@@ -94,7 +94,7 @@ docs/                # Coding convention docs
 ### Error Handling
 - **No C++ exceptions** — some builds disable them
 - Use return codes (`false`, `-1`) and global flags (`errorFlag = ERR_LOW_MEM`)
-- Use early returns as guard clauses: `if (!enabled || strip.isUpdating()) return;`
+- Use early returns as guard clauses: `if (!enabled || (strip.isUpdating() && (millis() - last_time < MAX_USERMOD_DELAY))) return;`
 - Debug output: `DEBUG_PRINTF()` / `DEBUG_PRINTLN()` (compiled out unless `-D WLED_DEBUG`)
 
 ### Strings and Memory