Skill: Implementation Docs Update Guide

Use this skill when finishing a phase, feature, or task that came from a development plan/prompt document (e.g. _IMPLEMENTATION_PLANS/*.md, docs/plans/*.md, or any "TODOS/spec" markdown), and the completed work must be recorded back into that document. Triggers: "update phase doc", "mark as done", "อัปเดตเอกสารการพัฒนา", "ปิด phase", "record status", or whenever a relevant plan document exists for the completed work.

Core Principle

The plan document is the single source of truth for what was requested AND what actually happened. Requirements stay untouched at the top; reality gets appended below. Never rewrite history — future readers must be able to diff spec vs. delivery.

Workflow

1. Find the source doc. The document the task originated from (search the project's plans/prompts directory). If none exists and the task was substantial, create one named like PHASE_<N>_<FEATURE>.md or <feature>-plan.md.
2. Do the work first. Code, migration, verification — complete before documenting.
3. Append the status section to the SAME document using the template below.
4. Never modify the original requirement lines. Not even typos. They are the record of what was asked.

Document Layout

## <FEATURE> TODOS <- original requirements, UNTOUCHED