When ECC is installed as a Claude Code plugin via the marketplace,
scripts live in the plugin cache (~/.claude/plugins/cache/...) but
commands fallback to ~/.claude/ which doesn't have the scripts.
Add resolve-ecc-root.js with a 3-step fallback chain:
1. CLAUDE_PLUGIN_ROOT env var (existing)
2. Standard install at ~/.claude/ (existing)
3. NEW: auto-scan the plugin cache directory
Update sessions.md and skill-health.md commands to use the new
inline resolver. Includes 15 tests covering all fallback paths
including env var priority, standard install, cache discovery,
and the compact INLINE_RESOLVE used in command .md files.
