Add a LICENSE — the repo is public but legally all-rights-reserved

[eaitbrahim]

The repository is public, but there is no LICENSE file. Under copyright law that means all rights reserved: nobody may legally fork it, modify it, or contribute to it, and anyone who does is exposed. This blocks every other issue in Phase 6–8.

Decide

option	why	why not
Apache-2.0 (recommended)	Explicit patent grant; explicit warranty disclaimer, which matters for software that moves money; business-friendly, so people can use it at work	Permits a closed hosted fork
AGPL-3.0	Prevents someone running keel-as-a-service without publishing changes	Deters exactly the contributors we want; many employers forbid it
MIT	Shortest, most familiar	No patent grant, thinner warranty disclaimer

Recommendation is Apache-2.0: the warranty disclaimer and patent grant matter more here than preventing a hosted fork, and the audience we want is individual developers who may be reading at work.

Acceptance

• LICENSE at repo root with the chosen text, copyright line, and year
• pyproject.toml declares the same licence (all six distributions)
• gh repo view --json licenseInfo reports it — GitHub must detect it, not just the file existing
• Decision and reasoning recorded in the file header or CONTRIBUTING.md, not left implicit

Until this closes

Do not accept external pull requests. A contributor has no rights to grant us and we have none to accept.