ci: speed up the Windows ARM64 unit test job

Installing dependencies took eight minutes there against one on x64.

Neither bufferutil nor utf-8-validate ships a win32-arm64 prebuild, so pnpm
compiled both with node-gyp on every cold install. Both fall back to
JavaScript when no binary is present, so skip their builds.

setup-node's pnpm cache restores on an exact lockfile hash, so a dependency
bump refetched the whole store on every runner. Hand the store cache to
pnpm/action-setup, which keys on the same hash but falls back to the last
store for the platform.

A cold setup step now takes 2m31s.

Author: EhabY

.github/actions/setup/action.yml

@@ -10,11 +10,15 @@ runs:
       run: git config --global url."https://github.com/".insteadOf "git@github.com:"
 
     - uses: pnpm/action-setup@ea17c68df8912ef543352723c149a84f56e3d413 # v6.1.0
+      with:
+        # Caches the pnpm store, keyed by lockfile hash with a prefix fallback,
+        # so a dependency bump reuses the rest of the store. setup-node's own
+        # pnpm cache restores on an exact hash only.
+        cache: true
 
     - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
       with:
         node-version: "22"
-        cache: "pnpm"
 
     - name: Install dependencies
       shell: bash

CONTRIBUTING.md

@@ -324,7 +324,8 @@ When updating the minimum Node.js version, update these files:
 
 Some dependencies are not directly used in the source but are required anyway.
 
-- `bufferutil` and `utf-8-validate` are peer dependencies of `ws`.
+- `bufferutil` and `utf-8-validate` are peer dependencies of `ws`. Their source
+  builds are off, so Windows on ARM64 uses their JavaScript fallback.
 - `ua-parser-js` and `dayjs` are used by the Coder API client.
 
 The coder client is vendored from coder/coder. Pin it to a release tag in

pnpm-workspace.yaml

@@ -32,13 +32,14 @@ dedupePeers: true
 
 allowBuilds:
   "@vscode/vsce-sign": true
-  bufferutil: true
+  # Only win32-arm64 lacks a prebuild, and its JavaScript fallback is fine.
+  bufferutil: false
   electron: true
   esbuild: true
   keytar: false
   odiff-bin: true
   unrs-resolver: true
-  utf-8-validate: true
+  utf-8-validate: false
 
 overrides:
   "@vscode-elements/elements": ^2.5.1