feat(tui): add config option to disable syntax highlighting in diffs

[ibrahimsag]

for #7853

Summary

Adds tui.diff_syntax config option to disable syntax highlighting in diffs.

{
  "tui": {
    "diff_syntax": false
  }
}

Default is true (syntax highlighting enabled). When set to false, diffs render without syntax highlighting.

Changes

• Added diff_syntax boolean option to TUI config schema
• Updated Edit component and permission dialog to respect the config
• Regenerated SDK types