* fix: skill-validator invocation for .github/plugin/plugin.json convention
The skill-validator --plugin mode looks for plugin.json at <dir>/plugin.json,
but external plugins (and the Copilot CLI) place it at .github/plugin/plugin.json.
This caused every external plugin with skills or agents to fail the skill-validator
gate with a misleading 'No plugin.json found' error, even when the install smoke
test passed correctly.
Extract buildSkillValidatorArgs() which reads plugin.json from
.github/plugin/plugin.json, resolves skills/agents paths relative to the plugin
root, and invokes skill-validator with --skills/--agents instead of --plugin.
Falls back to --plugin if the conventional path is not present.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
* fix: also check .plugins/plugin.json and root plugin.json locations
Extend buildSkillValidatorArgs to probe three candidate plugin.json locations
in priority order before falling back to --plugin:
1. .github/plugin/plugin.json (Copilot CLI convention)
2. .plugins/plugin.json
3. plugin.json (root — also the skill-validator's native --plugin expectation)
Extract findPluginJson() and PLUGIN_JSON_CANDIDATES constant so the list is easy
to extend. Paths in plugin.json are always resolved relative to the plugin root
regardless of where the manifest lives.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>