ci: produce OpenVSCode workbench assets for GHCR image

[tariqsaidofficial]

Fixes the WPCodeSpace OpenVSCode GHCR publish workflow so the image build produces and validates the browser workbench assets requested by the OpenVSCode runtime.

Problem:

• Published image responded over HTTP but rendered a blank page.
• Runtime logs showed missing:
  • /opt/openvscode-server/out/vs/code/browser/workbench/workbench.css
  • /opt/openvscode-server/out/nls.messages.js
  • /opt/openvscode-server/out/nls.messages.json
• Previous discovery showed NLS assets were produced, but workbench.css candidates were empty.

Changes:

• Add compile-build and minify-vscode-reh-web before packaging.
• Keep vscode-reh-web and vscode-web packaging steps.
• Expand CI diagnostics for workbench CSS candidates.
• Select a web asset source only if it has workbench CSS, nls.messages.js, and nls.messages.json.
• Validate required assets in Docker context.
• Validate required assets inside the built image.
• Curl root, workbench CSS, NLS JS, and NLS JSON during smoke test.
• Fail on any File not found or NLS read error in container logs.

Preserved:

• No pull_request trigger.
• No latest tag.
• Immutable tags only.
• YAML-safe Dockerfile generation.
• Generated bundle guard.

Local validation:

• YAML parsed successfully.
• No pull_request or latest match.
• Workflow-only diff.
• git diff --check passed.