Explain: add hooks and skills to guide the Claude Code plugin better

explain/claude_code_plugin/.claude-plugin/plugin.json

@@ -12,5 +12,18 @@
       "command": "${CLAUDE_PLUGIN_ROOT}/run.sh",
       "args": []
     }
+  },
+  "hooks": {
+    "PreToolUse": [
+      {
+        "matcher": "Bash",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/explain/claude_code_plugin/hooks/check_debugger_usage.sh"
+          }
+        ]
+      }
+    ]
   }
 }

explain/claude_code_plugin/hooks/check_debugger_usage.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+#
+# Block direct invocation of `udb`, `live-record`, `undo`, or opening `.undo` files.
+# These should only be used via the plugin's MCP tools.
+
+set -euo pipefail
+
+# Check if `jq` is available; if not, skip checks and allow the command.
+if ! command -v jq &> /dev/null; then
+    exit 0
+fi
+
+# Read JSON input from stdin.
+input=$(cat)
+command=$(echo "$input" | jq -r '.tool_input.command // ""')
+
+# Block direct `udb` invocation.
+if echo "$command" | grep -qE '\budb\b'; then
+    echo '{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"deny","permissionDecisionReason":"Use the /debug command or MCP debugging tools instead of invoking udb directly."}}'
+    exit 0
+fi
+
+# Block direct `live-record` invocation (including architecture-specific variants like `live-record_x64`).
+if echo "$command" | grep -qE '\blive-record(_[a-z0-9]+)?\b'; then
+    echo '{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"deny","permissionDecisionReason":"Use the /record command or the record MCP tool instead of invoking live-record directly."}}'
+    exit 0
+fi
+
+# Block direct access to `.undo` recording files (check before `undo` to get the right message).
+if echo "$command" | grep -qE '\.undo\b'; then
+    echo '{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"deny","permissionDecisionReason":"Do not access Undo recordings directly. Use the /debug command or MCP debugging tools."}}'
+    exit 0
+fi
+
+# Block direct `undo` invocation.
+if echo "$command" | grep -qE '\bundo\b'; then
+    echo '{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"deny","permissionDecisionReason":"Use the plugin commands (/debug, /record) or MCP tools instead of invoking undo directly."}}'
+    exit 0
+fi
+
+# Allow other commands.
+exit 0

skills/debugging-with-undo/SKILL.md

@@ -0,0 +1,46 @@
+---
+name: debugging-with-undo
+description: >
+  Debug programs using Undo time travel debugging. Record flaky tests, intermittent failures,
+  race conditions, or bugs that don't reproduce reliably. Analyze recordings by traveling
+  backwards through execution history. Use when the user mentions debugging, flaky tests,
+  intermittent bugs, race conditions, `.undo` files (Undo recordings), or asks why something
+  happened in an actual run. This can provide similar results as adding logging statements,
+  but without modifying the code or needing to re-run the program multiple times.
+---
+
+# Debugging with Undo time travel debugger
+
+Undo provides time travel debugging for Linux programs. This Skill guides you to:
+1. **Record** program execution to capture failures (especially intermittent ones)
+2. **Debug** recordings by traveling backwards through execution history
+
+## When to record (use `record` MCP tool)
+
+Record program execution when the user:
+- Has a **flaky test** or **intermittent failure** that doesn't reproduce reliably
+- Mentions **race conditions**, **threading issues**, or **concurrency bugs**
+- Wants to **capture a failure** for later analysis
+- Needs **deterministic replay** of a bug
+
+Undo captures the exact execution including thread interleavings, making even race conditions
+reproducible.
+
+## When to debug (use debugging MCP tools)
+
+Debug a recording when the user:
+- Has a **`.undo` recording file** to investigate
+- Asks **"why did this happen"** or **"how did this value get set"**
+- Wants **root cause analysis** on a captured failure
+- Needs to understand execution **backwards** from a crash or assertion
+
+## Workflow
+
+1. **If no recording exists**: Use `record` MCP tool to capture the failure
+2. **If recording exists**: Use debugging MCP tools to analyze it
+3. **Work backwards**: Start at the end (where the bug manifested), trace backwards
+
+## Important
+
+- **Never access `.undo` files directly** - they are opaque binary recordings
+- **Never invoke `udb`, `live-record`, or `undo` via Bash** - use the Undo MCP tools