fix: add missing Bun setup and dependency install to release job

The release job runs `node scripts/merge-mac-update-manifests.ts` but was
missing the Setup Bun and Install dependencies steps that every other job
in the workflow includes. While the script currently only uses Node built-ins,
this is inconsistent with the rest of the workflow and fragile if any npm
dependency is added to the script in the future.

Author: cursoragent

.github/workflows/nightly-release.yml

@@ -260,11 +260,19 @@ jobs:
         with:
           ref: ${{ needs.preflight.outputs.ref }}
 
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version-file: package.json
+
       - name: Setup Node
         uses: actions/setup-node@v6
         with:
           node-version-file: package.json
 
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
       - name: Download all desktop artifacts
         uses: actions/download-artifact@v8
         with: