Add editor open evidence primitive

[chubes4]

Summary

• Add wordpress.editor-open, a focused generic block editor primitive that opens post/site/explicit editor targets.
• Capture replayable editor evidence artifacts: step trace, DOM snapshot, screenshot, console/errors, and fixed WordPress editor store state.
• Register editor-state artifacts in manifests/review summaries and add a focused editor-open smoke test.

Refs #459

Verification

• npm run build
• npm run command-registry-smoke
• npm run editor-open-artifact-smoke

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Implemented the generic editor-open primitive, evidence artifact plumbing, and smoke coverage; Chris remains responsible for review and merge.