marketplace.git clones successfully but only publishes the partner-registered MCP server, omitting all manually-registered assets (eastus)

## Description

The plugin marketplace endpoint is enabled and `marketplace.git` clones successfully — but it only contains the **one MCP server that was registered via the Discovery > MCP partner path**. All **manually-registered** assets (two MCP servers + one Plugin that bundles them) are absent from the git repo, even though all four are visible in the portal and readable via the data API.

This is distinct from #80 (where `marketplace.git` 404s on every path) — here the repo **is** generated and served, just with incomplete contents. It may be related to the same data-plane rollout as #79 (`/v0.1/servers` 404 fix, reportedly landed to all regions 2026-06-25), since this is the same East US data-plane surface.

## Environment

- API Center, region **East US** (`.data.eastus.azure-apicenter.ms`)
- SKU: **Free**
- Plugin marketplace endpoint: **enabled** (Data API settings)
- Visibility conditions: none set (Specification format / API version lifecycle / Asset type all open)

## Inventory (all four visible in the portal)

| Asset | Type | Registration path | Lifecycle |
|---|---|---|---|
| Microsoft docs | MCP | Discovery > MCP partner list | Production |
| Azure DevOps MCP – EPIC | MCP | Manual | Production |
| Work IQ MCP | MCP | Manual | Production |
| MCP Toolkit | Plugin (bundles the 3 above) | Manual | Design |

## Reproduction steps

1. Register MCP servers manually via **Register an asset > MCP server** (Production lifecycle, valid remote + definitions).
2. Register a Plugin manually via **Register an asset > Plugin**, bundling those MCP servers.
3. Enable the **Plugin marketplace endpoint**.
4. Clone the marketplace repo:

git clone …/workspaces/default/plugins/marketplace.git

## Expected behavior

`marketplace/plugins/` contains a folder for **every** plugin/asset in the inventory.

## Actual behavior

`marketplace/plugins/` contains only `msdocs-mcp-server` — the single partner-registered server. The two manually-registered MCP servers and the manually-created Plugin never appear. Reproduced repeatedly over multiple hours with fresh clones; the change has persisted well beyond any propagation window.

## Questions

1. **What determines whether an asset is published to `marketplace.git`?** Is there required backing metadata (e.g. `plugin.json` / `.mcp.json`) that the Discovery-partner path generates automatically but manual registration does not?
2. **Is this a Free SKU limitation?**
3. **Plugin lifecycle:** The Plugin asset is stuck at **Design** (the registration form has no Lifecycle field). "Add version" on a plugin returns `API versions cannot be created or updated for APIs of kind 'plugin'. Use the dedicated plugin API instead.` There is no `az apic plugin` command group. **How do we set a Plugin asset's lifecycle stage** — and could the Design stage be why it's excluded from the marketplace?
4. Does the **Build 2026 GA** build change any of this behavior?

## Related

- #80 — marketplace.git 404s entirely (this issue differs: repo serves, contents incomplete)
- #79 — data-plane `/v0.1/servers` 404 fix (same region/surface)