Shorten double-tap reaction delay by 20%

[AbdulKus]

What changed

• reduce the message double-tap window to 80% of Android's system timeout
• use the same shortened timeout for both reaction recognition and delayed single-tap menu opening

On devices using Android's typical 300 ms timeout, the message menu now opens after about 240 ms.

Validation

• git diff --check
• remote blob and tree SHAs exactly match the local commit