Initial commit: todo app guide with 5 prompts and examples

Complete companion repo for "Your First Hour with Claude Code" article.
Includes step-by-step prompts, example output, troubleshooting, and cost guide.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

prompts/02-add-categories.md

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+# Prompt 02: Add Categories
+
+Copy and paste this into Claude Code:
+
+---
+
+Add color-coded categories to the todo app. Requirements:
+
+- Four categories: Work (blue #5B9FD6), Personal (green #4DB8A4), Health (orange #E87020), Learning (purple #A87BDB)
+- When adding a task, show a dropdown to pick the category
+- Each task shows a small colored dot or badge indicating its category
+- Add filter buttons at the top: "All", "Work", "Personal", "Health", "Learning"
+- Clicking a filter shows only tasks in that category
+- "All" shows everything
+- Active filter button should be visually highlighted
+- Categories are saved in localStorage along with the tasks
+- Keep the existing dark mode design
+
+---
+
+## What Happens
+
+Claude Code reads the existing `index.html`, understands the current structure, and adds the category system without breaking anything that already works.
+
+This is the agent loop in action: it does not start from scratch. It reads what exists, plans the changes, and edits precisely.
+
+## What to Expect
+
+- A category dropdown appears next to the task input
+- Colored filter buttons appear above the task list
+- Each task shows its category color
+- Switching filters instantly shows/hides tasks
+- Old tasks (without categories) still work