fix(editor): opt editors out of macOS Writing Tools suggestions

A "Write with Siri" pill appears over empty editors on the macOS 27 beta,
because Codemirror's contentDOM is a contenteditable like any other. The
`writingsuggestions` attribute opts an editable element out, and setting
it here covers every editor at once.

If the pill turns out to be separate from writing suggestions, the
remaining lever is WKWebView's writingToolsBehavior, which would disable
Writing Tools for the whole window.

apps/yaak-client/components/core/Editor/Editor.tsx

@@ -601,6 +601,8 @@ function getExtensions({
     EditorView.contentAttributes.of({
       autocapitalize: "off",
       autocorrect: "off",
+      // Keeps macOS Writing Tools from offering to write code for us
+      writingsuggestions: "false",
     }),
     EditorView.domEventHandlers({
       focus: () => {