1. Just a single sentence idea or even copying the relevant messages from chat or email. If you are using Jira or similar, this is where MCP gets useful.

2. Only Claude at the moment

3. Each has its own repo and own CLAUDE.md/AGENTS.md file. The CLAUDE.md file is just a lookup document.

The detailed project specific markdown are under the rules folder, e.g. "forms-and-dialogs.md", "roles.md", etc. These rules are always updated by the agent for all new features/bug fixes, etc.

I also instruct the agent to always keep detailed markdown in the docs folder, which is subdivided into: idea/plan/review. These get created when new features or other significant updates are implemented.

4. The agent so far has not failed to reference the above files, so it already knows what approach to do when working on a new task.

5. I built my own skills framework for this (inspired by Superpowers) and still using it.