fix(fabric): implement missing TextInput commands for macOS

[Saadnajmi]

Summary

• Add setGhostText command to Fabric TextInput — was declared in JS supportedCommands but completely missing from the native Fabric command handler (RCTTextInputNativeCommands.h). Ported full implementation from Paper (RCTBaseTextInputView.mm) with Fabric API adaptations.
• Fix setTextAndSelection on macOS — changed notifyDelegate:YES to notifyDelegate:NO to match Paper behavior, preventing spurious delegate callbacks during programmatic selection changes from JS.
• Add ghost text cleanup in delegate methods — strips ghost text in textInputDidChange when user types, preventing ghost text from leaking into JS state.
• Add debug logging — temporary __DEV__ logging in setLocalRef to help diagnose the reported ref-is-null issue at runtime.
• Add RNTesterPlayground verification — interactive test case with buttons for all TextInput ref commands (focus, blur, clear, setSelection, setGhostText) and ref status display.

Test plan

• Build macOS RNTester with Fabric, navigate to Playgrounds → Playground
• Verify "Ref status" shows "REF OK" (not "REF IS NULL")
• Test each button: Focus, Blur, Clear, Set Selection (0,5), Set Ghost Text, Clear Ghost Text
• Verify typing into TextInput clears active ghost text
• Verify setSelection sets selection without triggering extra selection change events
• Run jest TextInput-test.js — new assertions for setSelection and setGhostText instance methods
• Remove debug logging in TextInput.js before merging

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