fix: dispatch Ctrl+V via tunnel preview so editor paste works

[fuzzzerd]

Summary

Closes #197.

The Window-level KeyBinding for PasteFileMakerClipData consumed Ctrl+V before the focused text editor could see it, so plain-text copy/paste inside the script editor and the search box was broken — the global FileMaker-clip paste fired instead.

Fix

Replaced the XAML KeyBinding with a tunnel-phase preview handler in MainWindow code-behind. The handler walks the focused element up the visual tree:

• Focus is inside a TextBox / TextEditor / TextArea → no-op, the editor handles Ctrl+V natively.
• Focus is anywhere else (tree, tabs, window background) → consume the key and invoke vm.PasteFileMakerClipData().

Tunnel phase is required because text editors mark Ctrl+V handled in their own KeyDown, so a bubble-phase override would never see the global case.

Why not the alternatives

• Clipboard-content dispatch (editors only handle Ctrl+V if clipboard has plain text): clipboard reads are async, and FileMaker writes both Unicode Text and Mac-XMSC on copy, so this would never disambiguate.
• Separate shortcut (e.g., Ctrl+Shift+V for global paste): cleanest design, but a UX change. Left as a future option.

The view concern (focus + routed-event dispatch) stays in code-behind; the action (PasteFileMakerClipData) remains in the VM.

[github-actions]

Test Results

✔️ Tests 1254 / 1254 - passed in 11.8s
✔️ Coverage 78.1% - passed with 70% threshold
📏 14368 / 16856 lines covered 🌿 4883 / 7794 branches covered
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✏️ updated for commit 5a343fa