[codex] Record Mirror Codex UI visibility evidence

[YSCJRH]

Summary

• Record direct Codex app UI evidence that the globally installed Mirror Codex plugin is visible as Mirror Codex.
• Keep the evidence boundary explicit: the screenshot proves UI visibility, while Market install controls and a full Mirror Demo prompt-response workflow remain TODO[verify].
• Clarify that the observed Chinese 完全访问权限 UI text is session UI text, not a reinterpretation of the plugin manifest capability, which remains Read.

Validation

• ./make.ps1 plugin-release-check
• python -m pytest backend\tests\test_api.py -q
• git diff --check

No frontend files changed, so npm run build --prefix frontend was not run.