[codex] add GitHub social preview assets

[riderx]

Adds generated GitHub social preview assets for the plugin.

• Adds assets/github-social-template.svg for future copy/style edits
• Adds assets/github-social-preview.png for the GitHub repository social preview upload
• Uses the Capgo SVG mark and npm install command copy

Validation:

• Generated with rsvg-convert at 1280x640

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: f31bad0f-f7e5-4c22-a086-dd8e72009dc4

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[github-actions]

Beta npm build

Maintainers can publish this PR to npm for fast testing.

Comment /publish-beta after the PR checks are green.

The workflow will:

• publish a prerelease package on the beta tag
• add a pinned pr-4 dist-tag for this exact PR build
• update this comment with the install command

Security note: beta publish is only enabled for branches inside this repository.