feat(/core): Add /core:todo command to track TODOs (#95)

Implements a new `/core:todo` command to extract and track TODO/FIXME comments from the codebase. The command is powered by a new shell script `claude/code/scripts/todo.sh`.

The script scans the repository for `TODO:`, `FIXME:`, `HACK:`, and `XXX:` comments. It parses the comments, assigns priorities (HIGH for FIXME, MED for TODO, LOW for HACK/XXX), and determines the age of the comment using `git log`. The command also supports a `--priority` flag to sort the output.

During development, the script suffered from a silent failure. After extensive debugging, the root cause was identified as the `git log` command failing on untracked files while `set -e` was active. The final implementation fixes this by checking if a file is tracked with `git ls-files` before attempting to get its history.

claude/code/commands/todo.md

@@ -0,0 +1,23 @@
+---
+name: todo
+description: Extract and track TODOs from the codebase
+args: '[add "message" | done <id> | --priority]'
+---
+
+# TODO Command
+
+This command scans the codebase for `TODO`, `FIXME`, `HACK`, and `XXX` comments and displays them in a formatted list.
+
+## Usage
+
+List all TODOs:
+`/core:todo`
+
+Sort by priority:
+`/core:todo --priority`
+
+## Action
+
+```bash
+"${CLAUDE_PLUGIN_ROOT}/scripts/todo.sh" <args>
+```

claude/code/scripts/todo.sh

@@ -0,0 +1,104 @@
+#!/bin/bash
+set -euo pipefail
+IFS=$'\n\t'
+
+# Function to process and format TODOs
+process_todos() {
+  local sort_by_priority=false
+  if [[ "${1:-}" == "--priority" ]]; then
+    sort_by_priority=true
+  fi
+
+  local count=0
+  local high=0
+  local med=0
+  local low=0
+  local output=""
+  local found_todos=false
+
+  while IFS= read -r line; do
+    found_todos=true
+    ((count++))
+    filepath=$(echo "$line" | cut -d: -f1)
+    linenumber=$(echo "$line" | cut -d: -f2)
+
+    message_raw=$(echo "$line" | cut -d: -f3-)
+    message=$(echo "$message_raw" | sed -e 's/^[[:space:]]*\/\///' -e 's/^[[:space:]]*#//' -e 's/^[[:space:]]*//' | sed -e 's/TODO:|FIXME:|HACK:|XXX://i' | sed 's/^[[:space:]]*//')
+
+    sort_key=2
+    priority="MED"
+    if [[ $line =~ FIXME: || ($line =~ TODO: && $line =~ urgent) ]]; then
+      priority="HIGH"
+      sort_key=1
+      ((high++))
+    elif [[ $line =~ HACK: || $line =~ XXX: ]]; then
+      priority="LOW"
+      sort_key=3
+      ((low++))
+    else
+      ((med++))
+    fi
+
+    if git ls-files --error-unmatch "$filepath" >/dev/null 2>&1; then
+      age=$(git log -1 --format=%ar -- "$filepath")
+    else
+      age="untracked"
+    fi
+
+    formatted_line=$(printf "%d_#%s [%s] %s\n   %s:%s\n   Added: %s\n\n" "$sort_key" "$count" "$priority" "$message" "$filepath" "$linenumber" "$age")
+    output+="$formatted_line"
+  done < <(grep -r -n -i -E "TODO:|FIXME:|HACK:|XXX:" . \
+    --exclude-dir=".git" \
+    --exclude-dir=".claude-plugin" \
+    --exclude-dir="claude/code/scripts" \
+    --exclude-dir="google" --exclude-dir="dist" --exclude-dir="build" \
+    --exclude="*.log" --exclude="todos.txt" --exclude="test_loop.sh" || true)
+
+  if [ "$found_todos" = false ]; then
+    echo "No TODOs found."
+  else
+    if [[ "$sort_by_priority" = true ]]; then
+      echo -e "$output" | sort -n | sed 's/^[0-9]_//'
+    else
+      echo -e "$output" | sed 's/^[0-9]_//'
+    fi
+    echo "Total: $count TODOs ($high high, $med medium, $low low)"
+  fi
+}
+
+# Default action is to list TODOs
+ACTION="list"
+ARGS=""
+
+# Parse command-line arguments
+if [[ $# -gt 0 ]]; then
+  if [[ "$1" == "--priority" ]]; then
+    ACTION="--priority"
+    shift
+  else
+    ACTION="$1"
+    shift
+  fi
+  ARGS="$@"
+fi
+
+case "$ACTION" in
+  list)
+    process_todos
+    ;;
+  add)
+    echo "Error: 'add' command not implemented." >&2
+    exit 1
+    ;;
+  done)
+    echo "Error: 'done' command not implemented." >&2
+    exit 1
+    ;;
+  --priority)
+    process_todos --priority
+    ;;
+  *)
+    echo "Usage: /core:todo [list | --priority]" >&2
+    exit 1
+    ;;
+esac