[KrazyArcher]

Fixes #307

Summary

• Separates initial sendMessage(content) calls (which reset retryCountRef.current = 0) from internal executeSend(content, true) retry invocations so retryCountRef.current increments up to maxRetries instead of resetting on every retry.
• Ensures linear backoff (retryDelay * retryCountRef.current) progresses as 1x, 2x, ... maxRetries and stops after maxRetries attempts.
• Catches background promise rejections inside the setTimeout auto-retry callback to prevent unhandled promise rejections while still updating error state and calling onError.

Verification

• node --test pkg/react/src/hooks/useMessage.test.mjs -> Passed ✅