macOS Chat Fixes

Fixes Minecraft's text fields (chat, sign editing, world names, search boxes, etc.) to behave like a native macOS text field: proper ⌘ and ⌥ arrow key navigation, word-aware selection, and macOS-style deletion instead of Windows/Linux key bindings pretending to be Mac shortcuts.

The problem

Vanilla Minecraft only really understands one set of non-Mac text shortcuts: Ctrl+Arrow to jump by word, Ctrl+A/C/V/X for select/copy/paste/cut. On macOS, it maps ⌘ onto those same Ctrl-shaped shortcuts which gets arrow navigation wrong. On macOS:

• ⌘ + Left/Right should jump to the start/end of the line.
• ⌥ + Left/Right should jump by word, vanilla doesn't bind this at all on Mac.

This mod fixes all of that, without touching anything on Windows or Linux.