fix: respect metadata.pluginRoot + prepare v0.8.9 hotfix

[danielmeppiel]

Problem

apm install azure-cloud-development@awesome-copilot fails:

[x] github/awesome-copilot/azure-cloud-development -- not accessible or doesn't exist

The actual package lives at github/awesome-copilot/plugins/azure-cloud-development.

Root Cause

The upstream awesome-copilot marketplace.json declares:

{
  "metadata": { "pluginRoot": "./plugins" },
  "plugins": [
    { "name": "azure-cloud-development", "source": "azure-cloud-development" }
  ]
}

pluginRoot tells consumers that bare-name plugin sources resolve under plugins/. Our parser never read this field, so "source": "azure-cloud-development" resolved to github/awesome-copilot/azure-cloud-development (missing plugins/ prefix).

Fix

• models.py — Added plugin_root: str to MarketplaceManifest, parsed from metadata.pluginRoot
• resolver.py — _resolve_relative_source() prepends plugin_root to bare-name sources (no /); threaded through resolve_plugin_source() and resolve_marketplace_plugin()
• Tests — 10 new test cases covering pluginRoot parsing, bare-name resolution with/without root, path sources bypassing root

Release v0.8.9

• CHANGELOG.md — v0.8.9 section with fix: respect metadata.pluginRoot + prepare v0.8.9 hotfix #512 and fix: CI test assertions for Rich line-wrapping and scope output #510 fixes
• pyproject.toml — version bumped to 0.8.9

All 3398 unit tests pass.

[Copilot]

Pull request overview

Adds support for metadata.pluginRoot in marketplace manifests so that bare-name plugin sources (e.g., "source": "azure-cloud-development") resolve under the configured root directory (e.g., ./plugins) when installing from marketplaces like github/awesome-copilot.

Changes:

• Extend MarketplaceManifest to parse and store metadata.pluginRoot as plugin_root.
• Thread plugin_root through marketplace source resolution and apply it to bare-name relative sources.
• Add unit tests covering parsing and resolution behavior with/without pluginRoot.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

File	Description
tests/unit/marketplace/test_marketplace_resolver.py	Adds coverage for bare-name relative source resolution with plugin_root.
tests/unit/marketplace/test_marketplace_models.py	Adds coverage for parsing metadata.pluginRoot into manifest.plugin_root.
src/apm_cli/marketplace/resolver.py	Threads plugin_root into resolution logic and prefixes bare-name sources when configured.
src/apm_cli/marketplace/models.py	Stores plugin_root on the manifest and parses it from metadata.pluginRoot.