#2067 feat: add select all text action

[keymapper-ai]

Summary

• add a new SELECT_ALL_TEXT action and ActionData.SelectAllText
• wire action metadata, creation, UI title, and persistence mapping (select_all_text)
• execute via accessibility ACTION_SET_SELECTION from 0 to focused text length and update changelog

Test plan

• Build and run on device/emulator
• Add new key map action: Keyboard > Select all text
• Focus text input and trigger action to confirm full selection
• Verify existing Select word at cursor still works