ci: publish WPCodeSpace OpenVSCode image to GHCR

[tariqsaidofficial]

Adds a publish-only GHCR workflow for the WPCodeSpace OpenVSCode image.

Scope:

• Adds .github/workflows/wpcodespace-ghcr-publish.yml.
• Publishes only from workflow_dispatch or push to main.
• Does not publish from pull_request.
• Builds the same runtime path proven by the existing WPCodeSpace image validation workflow.
• Smoke-tests the container before pushing.
• Publishes immutable tags only:
  • ghcr.io/dxbmark/wpcodespace-openvscode:sha-${GITHUB_SHA}
  • ghcr.io/dxbmark/wpcodespace-openvscode:${GITHUB_SHA::12}
• Does not publish latest.
• Aligns the chat agent hover test copy with the WPCodeSpace chat mode copy.

Validation before PR:

• YAML parses successfully.
• No pull_request trigger.
• No latest tag.
• Generated Dockerfile is written through a YAML-safe Python writer.
• Generated bundle guard remains in place.