Clean up README and other documentation

[nathanjcochran]

This cleans up the README in preparation for making the repo public.

In particular, it:

• Moves most internal development info out of the README and into a new docs/development.md file (which is still referenced from the "Contributing" section of the README).
• Moves the "installation instructions and "Quick Start" to the top of the README
• Explains the MCP server and how to install it
• Documents all of the available commands and MCP tools
• Documents all of the configuration options, env vars, and flags

I also moved some other files into the new docs folder (in particular, DECISIONS.md and CODE_REVIEW.md) and removed the TODO.md file (which looked stale/outdated to me, especially now that we're tracking everything in Linear). I figure we want the top-level to be as clean and organized as possible.

Finally, I made a bunch of updates to the CLAUDE.md file (which is still at the top-level). Some of it was just getting existing information accurate and up-to-date (like the project structure/architecture), and the rest was to reflect new patterns and additions to the codebase (like the MCP server and the release pipeline).

Open to any and all feedback on this!

Closes AGE-127.

[linear]

AGE-127 Tiger CLI: Clean up repo and make it public

We intend to open-source this. Before making the repo public, we should make sure everything is in a good state (READMEs and other documentation are up-to-date and accurate, etc.)

See also this Slack conversation.

[cevian]

looks great

[Askir]

Looks great. Just small comments.

Using "Tiger" without specifying Tiger Data or Tiger Cloud or Tiger CLI by itself feels odd to me.