Add Codex plugin manifest schema

[Nick2bad4u]

Summary

Adds a SchemaStore schema for Codex plugin manifests at .codex-plugin/plugin.json.

This is the correct schema surface for OpenAI Codex PR #29488, which added dark-mode plugin logo metadata. The existing codex-skill-metadata.json schema covers agents/openai.yaml skill metadata; that skill metadata surface still does not expose plugin interface.logoDark.

This schema includes:

• interface.logoDark for local package-relative dark-mode logo assets
• local plugin interface fields from the Codex plugin manifest validator
• negative fixtures for invalid logoDark values
• negative fixtures showing that app-server/remote-catalog fields such as logoUrlDark are not accepted in local plugin.json
• a negative fixture for unsupported top-level hooks, matching the bundled validator's accepted manifest keys

Sources

• [plugins] Add dark-mode logo metadata openai/codex#29488
• https://github.com/openai/codex/blob/main/codex-rs/plugin/src/manifest.rs
• https://github.com/openai/codex/blob/main/codex-rs/core-plugins/src/manifest.rs
• https://github.com/openai/codex/blob/main/codex-rs/skills/src/assets/samples/plugin-creator/scripts/validate_plugin.py
• https://github.com/openai/codex/blob/main/codex-rs/skills/src/assets/samples/plugin-creator/references/plugin-json-spec.md

Validation

• node .\cli.js check --schema-name=codex-plugin-manifest.json
• npm run prettier -- --cache --ignore-unknown .\src\schemas\json\codex-plugin-manifest.json .\src\api\json\catalog.json .\src\test\codex-plugin-manifest\plugin.json .\src\test\codex-plugin-manifest\inline-mcp.json .\src\negative_test\codex-plugin-manifest\invalid-logo-dark-type.json .\src\negative_test\codex-plugin-manifest\remote-logo-url-dark.json .\src\negative_test\codex-plugin-manifest\unsupported-hooks-field.json

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.