Add Codex plugin metadata and Svix Skill evals

[rforgeon]

Summary

• add Codex-compatible plugin metadata for the existing Svix Skills package
• document the plugin vs Skill distinction in the README
• add JSONL eval cases for Dispatch planning, webhook receiver review, and CLI quickstart verification

The plugin is the installable package for agent workspaces. Each Svix Skill remains a focused SKILL.md workflow inside that plugin.

Privacy / telemetry

The eval docs explicitly avoid prompts, source files, webhook payloads, API keys, signing secrets, tenant identifiers, tool arguments, and model outputs.

Validation

node -e "JSON.parse(require('fs').readFileSync('.codex-plugin/plugin.json','utf8')); const lines=require('fs').readFileSync('evals/svix-agent-skills/cases.jsonl','utf8').trim().split(/\n/); lines.forEach(JSON.parse); console.log('valid plugin json and jsonl lines='+lines.length);"

Output:

valid plugin json and jsonl lines=3

[svix-pluiz]

Hey @rforgeon, thanks for contributing!
Before we merge this, could you address my comments?

[svix-pluiz]

As we're not using Telvine, could you remove this section?

Suggested change

	## Telvine packaging
	If this plugin is published through Telvine, publish the repository as the plugin
	and treat each Svix Skill as a plugin component:
	```bash
	npm i -g telvine
	telvine login
	telvine publish .
	```

[svix-pluiz]

Could you explain where and when this skill eval script is meant to run? It feels like this is out of the scope for this project

[rforgeon]

Thanks for the review. I pushed e151b42 addressing both points:

• removed the Telvine packaging sections from the README and eval README
• clarified that the JSONL evals are seed cases for external agent harness validation, not a Svix runtime script or part of the repo's application test suite

I also revalidated the manifest and JSONL locally:

valid plugin json and jsonl lines=3