feat: add debug mode to capture agent tool log

When debug: true, the review comment includes a collapsible section
showing which files the agent read, grep patterns used, etc.
Also prints agent log on failure for easier troubleshooting.

scripts/review.sh

@@ -125,18 +125,40 @@ PROMPT="${PROMPT}
 The git diff is at /tmp/pi-diff.txt. Start by reading it, then read any files you need for full context."
 
 # Run Pi in print mode (non-interactive, no session persistence)
+# Capture stderr (tool call log) always — only show it when debug is on
 pi --no-session \
   ${PROVIDER_FLAG} \
   --model "${PI_MODEL}" \
   --tools "${PI_TOOLS}" \
   -p "${PROMPT}" \
-  > /tmp/pi-review.md 2>/dev/null
+  > /tmp/pi-review.md 2>/tmp/pi-agent.log
 
 if [ ! -s /tmp/pi-review.md ]; then
   echo "::error::Pi generated no output"
+  echo "Agent log (last 30 lines):"
+  tail -30 /tmp/pi-agent.log
   exit 1
 fi
 
+# If debug mode, append the agent's tool log to the review
+if [ "${PI_DEBUG}" = "true" ]; then
+  AGENT_LOG=$(sed 's/\x1b\[[0-9;]*m//g' /tmp/pi-agent.log | head -200)
+  cat >> /tmp/pi-review.md << LOGEOF
+
+---
+
+<details>
+<summary>🔍 <strong>Agent Tool Log</strong> (debug)</summary>
+
+\`\`\`
+${AGENT_LOG}
+\`\`\`
+
+</details>
+LOGEOF
+  echo "Debug: agent log appended to review"
+fi
+
 echo "Review generated successfully."
 echo "::endgroup::"