feat: initial companion repo for CC-010 CLAUDE.md

exercises/01-write-your-first.md

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+# Exercise 01: Write Your First CLAUDE.md
+
+**Concept:** CLAUDE.md (CC-010)
+**Level:** Basic
+**Time:** ~10 minutes
+
+---
+
+## Objective
+
+Write a CLAUDE.md for a real project you own. By the end of this exercise,
+Claude will know who you are, what the project does, and how you want it
+to behave -- automatically, every session.
+
+This is your first hands-on contact with CLAUDE.md. The only requirement
+is that you have a project directory with a few files in it.
+
+---
+
+## Before You Start
+
+Confirm you have:
+
+- [ ] Claude Code installed (`claude --version` prints a version)
+- [ ] A project directory you want to write a CLAUDE.md for
+- [ ] Claude Code open in that project directory
+
+This exercise works best in your own project. If you do not have one
+handy, open Claude Code in any directory that has at least a few files.
+
+---
+
+## Instructions
+
+**Step 1:** Navigate to your project and open Claude Code.
+
+```bash
+cd /path/to/your-project
+claude
+```
+
+Confirm there is no CLAUDE.md there yet:
+
+```bash
+ls CLAUDE.md
+```
+
+Expected output: `ls: CLAUDE.md: No such file or directory`
+
+If a CLAUDE.md already exists, pick a different project for this exercise
+or rename the existing one temporarily (`mv CLAUDE.md CLAUDE.md.bak`).
+
+**Step 2:** Think about three things before you run anything.
+
+- Who you are and what you care about when working on this project
+- What the project does in one sentence
+- Two or three rules that would save time if Claude knew them up front
+  (examples: "always use TypeScript", "never modify files in dist/", "prefer short functions")
+
+You do not need to write these down. Just have them in mind.
+
+**Step 3:** Paste this prompt into Claude Code:
+
+```
+Look at this project. Read the files here, then write a CLAUDE.md for it.
+
+The CLAUDE.md should include:
+1. What this project is (one short paragraph, 2-3 sentences max)
+2. How to work on it (language, framework, any tools)
+3. Three specific rules I want you to follow in every session
+
+For rule 3, use these rules I care about:
+- [replace this with your first rule, e.g. "Never use var, always use const or let"]
+- [replace this with your second rule, e.g. "All functions must have a JSDoc comment"]
+- [replace this with your third rule, e.g. "Do not modify package.json without asking first"]
+
+Keep it under 60 lines. No headers longer than one line. Plain and direct.
+```
+
+Replace the three placeholder rules with your own before pasting.
+
+**Step 4:** Review what Claude writes and ask for one change.
+
+Read the CLAUDE.md Claude produced. Find one thing that is off, vague, or
+missing, then ask Claude to fix it:
+
+```
+Change [the part that is wrong] to [what it should say].
+```
+
+This is a normal part of the process. CLAUDE.md files are written with
+Claude, not entirely by it.
+
+---
+
+## Expected Output
+
+After completing the steps above, you should see:
+
+- A `CLAUDE.md` file in your project root
+- It has a project description (not generic -- specific to your project)
+- It has your three rules stated clearly
+- It is under 60 lines total
+
+If Claude produced something generic or padded, ask it to be more specific
+and shorter. Generic CLAUDE.md files provide almost no value.
+
+---
+
+## What You Learned
+
+- **CLAUDE.md is a briefing, not a manual:** Give Claude the context it needs
+  to behave like a new colleague who already knows your project
+- **It is auto-loaded every session:** You never have to paste it in or say
+  "remember, we use TypeScript" again
+- **Write it with Claude, not for Claude:** Use Claude to read the project
+  and draft the file, then you correct and sharpen it
+
+---
+
+## Next
+
+Ready to see how CLAUDE.md files stack on top of each other? Move to
+[Exercise 02: Hierarchy in Action](./02-hierarchy-in-action.md).