refactor(cli): extract deprecation guard to helper module

Move the Node v23+ process.noDeprecation try/catch guard into
src/cli/update-cli/suppress-deprecations.ts so that update-cli.ts
does not grow past the 1000-line size-guard threshold.

No behavior change.

src/cli/update-cli.ts

@@ -62,6 +62,7 @@ import { formatCliCommand } from "./command-format.js";
 import { installCompletion } from "./completion-cli.js";
 import { runDaemonRestart } from "./daemon-cli.js";
 import { formatHelpExamples } from "./help-format.js";
+import { suppressDeprecations } from "./update-cli/suppress-deprecations.js";
 
 export type UpdateCommandOptions = {
   json?: boolean;
@@ -672,12 +673,7 @@ function printResult(result: UpdateRunResult, opts: PrintResultOptions) {
 }
 
 export async function updateCommand(opts: UpdateCommandOptions): Promise<void> {
-  try {
-    process.noDeprecation = true;
-  } catch {
-    /* read-only on Node v23+ */
-  }
-  process.env.NODE_NO_WARNINGS = "1";
+  suppressDeprecations();
   const timeoutMs = opts.timeout ? Number.parseInt(opts.timeout, 10) * 1000 : undefined;
   const shouldRestart = opts.restart !== false;
 

src/cli/update-cli/suppress-deprecations.ts

@@ -0,0 +1,16 @@
+/**
+ * Suppress Node.js deprecation warnings.
+ *
+ * On Node.js v23+ `process.noDeprecation` may be a read-only property
+ * (defined via a getter on the prototype with no setter), so the
+ * assignment can throw. We fall back to the environment variable which
+ * achieves the same effect.
+ */
+export function suppressDeprecations(): void {
+  try {
+    process.noDeprecation = true;
+  } catch {
+    // read-only on Node v23+; NODE_NO_WARNINGS below covers this case
+  }
+  process.env.NODE_NO_WARNINGS = "1";
+}