chore: drop canOverrideNativeFocus runtime probe

[layershifter]

Summary

canOverrideNativeFocus was a feature-detection helper that temporarily reassigned HTMLElement.prototype.focus to a no-op, called .focus() on a synthetic button, and checked whether the override fired. The result was cached in the module-level _canOverrideNativeFocus flag and gated the details.isFocusedProgrammatically write inside setupFocusEvent.

The probe guarded against pre-IE9 environments where prototype-level focus overrides were ignored. Every browser keyborg currently supports honours the override, so the flag is effectively always true after the first call.

Drops:

• the canOverrideNativeFocus function (~17 lines of synthetic-button-focus dance),
• the module-level _canOverrideNativeFocus flag,
• the lazy initialization branch inside setupFocusEvent.

The gated isFocusedProgrammatically write becomes unconditional:

// before
if (_canOverrideNativeFocus || data[LAST_FOCUSED_PROGRAMMATICALLY]) {
  details.isFocusedProgrammatically =
    target === data[LAST_FOCUSED_PROGRAMMATICALLY]?.deref();
  data[LAST_FOCUSED_PROGRAMMATICALLY] = undefined;
}

// after
details.isFocusedProgrammatically =
  target === data[LAST_FOCUSED_PROGRAMMATICALLY]?.deref();
data[LAST_FOCUSED_PROGRAMMATICALLY] = undefined;

Semantically identical when the override works, which is the only case still in scope.

Public API impact

None. canOverrideNativeFocus was module-private; _canOverrideNativeFocus was a module-private variable.

🤖 Generated with Claude Code

[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
keyborg All exports	3.974 kB 1.627 kB	3.765 kB 1.557 kB	-209 B -70 B
keyborg createKeyborg() & disposeKeyborg()	3.806 kB 1.586 kB	3.597 kB 1.514 kB	-209 B -72 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
keyborg KEYBORG_FOCUSIN constant	64 B 80 B

_{🤖 This report was generated against dfd7fe32327b37d8746c44aef6cebeda1ecc2397}