By C3 you have a clean BookTracker, a CLAUDE.md, path-scoped rules in .claude/rules/, a test-writer subagent, a PostToolUse build hook, and GitHub MCP wired up. Now you put it all to work on a feature that matters. Reading Progress tracks how far a reader is through a book — current page, status, and start/finish dates — governed by a small forward-only state machine. You'll write the spec first, build against it, test every rule, and finish with a deliberate debugging loop. Keep the conventions tight: this exact code becomes the agent tool in C6 and the MCP tool in C8, so IReadingProgressService is a stability contract, not throwaway Day 1 code.
