feat: introduce AI agent framework and task tooling

- add AGENT.md describing the agent system
- add AGENT_WORKFLOW.md defining the execution workflow
- add AI_TASK_TEMPLATE.md for structured task prompts
- add scripts/ai-task CLI tool for generating standardized agent tasks

scripts/ai-task

@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+
+# ai-task
+# Helper CLI to generate AI task prompts based on AI_TASK_TEMPLATE.md
+# Usage:
+#   scripts/ai-task build "Objective text" [scope...]
+#   scripts/ai-task plan "Objective text" [scope...]
+
+set -e
+
+TYPE="$1"
+OBJECTIVE="$2"
+shift 2 || true
+SCOPE=("$@")
+
+if [[ -z "$TYPE" || -z "$OBJECTIVE" ]]; then
+  echo "Usage: ai-task <plan|build> \"Objective\" [scope files...]"
+  exit 1
+fi
+
+TYPE_LOWER=$(echo "$TYPE" | tr '[:upper:]' '[:lower:]')
+TYPE_UPPER=$(echo "$TYPE_LOWER" | tr '[:lower:]' '[:upper:]')
+
+DATE=$(date "+%Y-%m-%d %H:%M")
+DAY=$(date "+%Y%m%d")
+
+case "$TYPE_LOWER" in
+  build)
+    PREFIX="BUILD"
+    ;;
+  plan)
+    PREFIX="PLAN"
+    ;;
+  *)
+    echo "Error: task type must be 'plan' or 'build'"
+    exit 1
+    ;;
+esac
+
+WORKLOG_FILE="docs/ai-worklog.md"
+LAST_SEQ=0
+
+if [[ -f "$WORKLOG_FILE" ]]; then
+  LAST_MATCH=$(grep -Eo "${PREFIX}-${DAY}-[0-9]{3}" "$WORKLOG_FILE" | tail -n 1 || true)
+  if [[ -n "$LAST_MATCH" ]]; then
+    LAST_SEQ=${LAST_MATCH##*-}
+    LAST_SEQ=$((10#$LAST_SEQ))
+  fi
+fi
+
+NEXT_SEQ=$(printf "%03d" $((LAST_SEQ + 1)))
+TASK_ID="${PREFIX}-${DAY}-${NEXT_SEQ}"
+
+# Build scope block
+cat <<EOF
+Task Type:
+${TYPE_UPPER}
+
+Task ID:
+${TASK_ID}
+
+Date:
+${DATE}
+
+Objective:
+${OBJECTIVE}
+
+Context:
+<describe repository state if needed>
+
+Scope:
+EOF
+
+if [ ${#SCOPE[@]} -gt 0 ]; then
+  for item in "${SCOPE[@]}"; do
+    printf '%s\n' "- ${item}"
+  done
+else
+  printf '%s\n' "- <fill scope>"
+fi
+
+cat <<EOF
+
+Requirements:
+<describe expected behavior>
+
+Constraints:
+- follow AGENT_WORKFLOW.md
+- keep scope minimal
+- preserve existing behavior unless explicitly changed
+
+Testing:
+<describe expected tests>
+
+Validation:
+make fix
+make quality
+
+Logging requirements:
+- append entry to docs/ai-worklog.md
+- append entry to docs/ai-prompts.md
+- include Date, Task ID, Agent, Scope
+- use Task ID: ${TASK_ID}
+
+Git requirements:
+- do NOT commit or push unless explicitly requested
+
+Expected Report:
+- files changed
+- behavior changes
+- validation results
+EOF