feat: add test command for CLAUDE_PLUGIN_ROOT variable substitution

Test command to verify if the fix in Claude Code 2.1.0 for
${CLAUDE_PLUGIN_ROOT} substitution works in inline bash execution.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cahaseler

commands/test-plugin-root.md

@@ -0,0 +1,21 @@
+---
+description: Test if ${CLAUDE_PLUGIN_ROOT} is substituted in bash execution
+allowed-tools: Bash(echo:*), Bash(ls:*), Bash(bun:*)
+---
+
+# Test Plugin Root Variable
+
+This command tests whether `${CLAUDE_PLUGIN_ROOT}` is properly substituted in bash execution.
+
+## Test 1: Inline echo (immediate execution)
+
+!`echo "Plugin root is: ${CLAUDE_PLUGIN_ROOT}"`
+
+## Test 2: List scripts directory (inline)
+
+!`ls "${CLAUDE_PLUGIN_ROOT}/skills/cc-track-tools/scripts/" 2>/dev/null || echo "FAILED: Cannot list scripts directory"`
+
+## Analysis
+
+If Test 1 shows the actual path (not the literal `${CLAUDE_PLUGIN_ROOT}`), the fix works.
+If it shows the literal string or empty, we still need the skill workaround.