fix(ci): scope node_modules cache key per job to stop save races

The Windows desktop build now succeeds (artifact builds + uploads), but the
job was marked failed on the post-job cache *save*: build-binaries
(windows-x64) and build-desktop-windows share runner.os/arch and thus the
same cache key, so concurrent saves hit "unable to reserve cache ... another
job may be creating this cache." Adding github.job to the key gives each job
its own cache and eliminates the race.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.changeset/fix-release-binary-publishing.md

@@ -5,7 +5,7 @@
 Fix the Binary Release workflow so platform binaries publish to GitHub Releases again:
 
 - The release job now tolerates a single failing build leg instead of being skipped, which previously suppressed all assets.
-- The node_modules cache key includes CPU arch so arm64 runners no longer restore x64 native deps (fixes the `@rollup/rollup-linux-arm64-gnu` build crash).
+- The node_modules cache key includes CPU arch (so arm64 runners no longer restore x64 native deps, fixing the `@rollup/rollup-linux-arm64-gnu` build crash) and the job id (so same-OS/arch jobs don't race on one key and fail the post-job cache save).
 - The macOS and Windows CLI signing steps are skipped gracefully when their certificate secrets are absent, so unsigned binaries still publish.
 - Desktop packaging now invokes `electron-builder` directly via `pnpm exec` instead of the `dist:*` scripts: pnpm leaked the `--` separator into script args, which made electron-builder ignore `--publish never` (auto-publishing to the wrong repo and 404ing) and drop the Linux `--x64 --arm64` flags.
 - The desktop build spawns workspace `.cmd` bins with a shell on Windows, fixing the `spawn EINVAL` failure.