Fix permission denied error by matching container user to runner UID/GID

When using manual docker run instead of container: block, GitHub Actions
no longer handles user mapping automatically. Files created by the
root-running container were unwritable by the host runner. Pass
--user $(id -u):$(id -g) to match the runner's identity.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: SukuWc

.github/workflows/electrical_workflow.yml

@@ -56,6 +56,7 @@ jobs:
           docker tag ghcr.io/${{ github.repository_owner }}/knot-electrical-builder:latest builder:local
         fi
         docker run -d --name builder \
+          --user $(id -u):$(id -g) \
           -v ${{ github.workspace }}:/work \
           -w /work \
           builder:local tail -f /dev/null

.github/workflows/mechanical_workflow.yml

@@ -60,6 +60,7 @@ jobs:
           docker tag ghcr.io/${{ github.repository_owner }}/knot-mechanical-builder:latest builder:local
         fi
         docker run -d --name builder \
+          --user $(id -u):$(id -g) \
           -v ${{ github.workspace }}:/work \
           -w /work \
           builder:local tail -f /dev/null