ci: install yarn on self-hosted runners and drop hosted cleanup step

Self-hosted runners don't ship yarn preinstalled the way GitHub-hosted
runners do, so 'yarn' was failing with command not found. Enable it via
corepack in the setup-node action. Also drop the cross-compile cleanup
step that removed /opt/hostedtoolcache, which is a GitHub-hosted-runner
path and fails with permission denied on self-hosted.

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

Author: djkazic

.github/actions/setup-node/action.yml

@@ -20,6 +20,10 @@ runs:
       with:
         node-version: '${{ inputs.node-version }}'
 
+    - name: enable yarn
+      shell: bash
+      run: corepack enable || npm install -g yarn
+
     - name: get yarn cache dir
       id: yarn-cache-dir
       shell: bash

.github/workflows/main.yml

@@ -115,9 +115,6 @@ jobs:
           - name: arm
             sys: darwin-arm64 linux-armv6 linux-armv7 linux-arm64
     steps:
-      - name: cleanup space
-        run: rm -rf /opt/hostedtoolcache
-
       - name: git checkout
         uses: actions/checkout@v4