fix(macos): TextInput Fabric commands - setGhostText, blur, and selection fixes

[Saadnajmi]

Summary

TextInput commands (setGhostText, blur, setSelection) don't work correctly under Fabric on macOS. This PR fixes three issues:

• Add missing setGhostText command to Fabric: Ghost text was implemented for Paper in [iOS/macOS] [TextInput] Implement ghost text #1890 / [iOS/macOS] [TextInput] Implement ghost text #1897 (with undo fixes in Ensure ghost text doesn't appear when performing undos #2105 / [0.73-stable] Ensure ghost text doesn't appear when performing undos #2106), but the Fabric command dispatcher and component view never got the implementation. This ports the ghost text logic (insertion, removal, attributes, delegate cleanup) from RCTBaseTextInputView to RCTTextInputComponentView.
• Fix blur command on macOS Fabric: blur was a silent no-op because it compared [window firstResponder] against the NSTextField, but on macOS the firstResponder during editing is the field editor (NSTextView), not the text field itself. Fixed by checking currentEditor on NSTextField.
• Fix ghost text being selectable on Fabric: Ghost text could be selected by the user on Fabric (but not Paper). Added cleanup in textInputDidChangeSelection to clear ghost text when the user changes selection, matching Paper behavior.
• Fix setTextAndSelection delegate notification: Changed notifyDelegate:YES to notifyDelegate:NO to match Paper's setSelectionStart:selectionEnd: behavior and prevent spurious delegate callbacks during programmatic selection changes.

Test plan

• Verified setGhostText command works via RNTester on macOS Fabric
• Verified blur command works on macOS Fabric
• Verified ghost text is not selectable on Fabric
• Verified focus, clear, setSelection commands still work
• JS TextInput tests pass

🤖 Generated with Claude Code

[nakambo]

Try undo\redo -- e.g.

• with ghost text showing (and valid undo record), perform undo -- check that ghost text goes away, and undo works as expected. Try redo.
• with ghost text showing do something to remove it (e.g. move IP), perform undo -- check ghost text doesn't come back. Try redo.
• try multiple undo\redo's, even when no valid record (check for ObjC exceptions being thrown\RN asserts firing)

[Saadnajmi]

Try undo\redo -- e.g.

• with ghost text showing (and valid undo record), perform undo -- check that ghost text goes away, and undo works as expected. Try redo.
• with ghost text showing do something to remove it (e.g. move IP), perform undo -- check ghost text doesn't come back. Try redo.
• try multiple undo\redo's, even when no valid record (check for ObjC exceptions being thrown\RN asserts firing)

As is, it blocks undos while ghost text is active. I think I'll leave it till we get further integration downstream.