Excel CLI discovery

The plugin does not place excelcli on PATH. Its launcher runs npx -y @sbroenne/excelcli@latest; do not assume a standalone executable is installed or restore the retired GitHub-release downloader.

For the plugin-bundled copy of this skill, ..\..\bin\start-cli.ps1 relative to the directory containing this SKILL.md locates the plugin launcher. For a standalone skill installation (including the skill ZIP), that relative path does not apply: the skill package does not contain the launcher. Locate the actual installed excel-cli plugin through the client's plugin listing and installation directory instead; do not resolve the launcher relative to the standalone skill. If the required plugin is absent, report that prerequisite rather than invoking a nonexistent file. Replace <plugin-root> below with that plugin's actual installed directory: