Add Claude Code marketplace manifest for phoenixvc plugins

[JustAGhosT]

Problem

Retort is referenced as a custom marketplace in Claude Code's extraKnownMarketplaces config, but there's no valid marketplace manifest published yet. This causes a startup error:

source: Invalid input

The extraKnownMarketplaces.phoenixvc.source field (whether as a nested object or flat string path) fails validation because retort doesn't expose the expected marketplace structure that Claude Code requires.

Current workaround

Removed extraKnownMarketplaces block and disabled retort@phoenixvc plugin in ~/.claude/settings.json.

Expected

Retort should publish a valid Claude Code marketplace manifest so that:

1. extraKnownMarketplaces can point to it
2. retort@phoenixvc resolves as a valid plugin
3. Mystira (and other onboarded repos) can consume retort's slash commands and quality gates via the plugin system

Context

• Claude Code expects a specific manifest format for custom marketplaces — needs investigation into the exact schema
• Related: mystira-workspace is pending retort onboarding (planned)
• The plugin/marketplace system may still be evolving on Claude Code's side — worth checking latest docs

Tasks

• Investigate Claude Code's extraKnownMarketplaces schema (what format does source expect?)
• Create a marketplace manifest in retort that satisfies the schema
• Test with extraKnownMarketplaces.phoenixvc.source pointing to retort
• Document the setup in retort's README

[blocksorg]

Mention Blocks like a regular teammate with your question or request:

@blocks can you add technical details to this issue?
@blocks make the following changes ...
@blocks create an issue from what was mentioned in the following comment ...
@blocks explain the following code ...
@blocks are there any security or performance concerns?

Run @blocks /help for more information.

Workspace settings | Disable this message