chore: add module, license and repository guides

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -1 +1,29 @@
 # corestack go
+
+Shared Go building blocks. The first one is `docs`, a checker for architecture decision records (ADRs) and implementation plans.
+
+## docs
+
+Install:
+
+```sh
+go install go.auvem.com/corestack/cmd/docs@latest
+```
+
+Use, from a repository root:
+
+```sh
+docs new adr "Use Example Queue for background jobs"   # creates docs/adr/<id>.md
+docs new plan "Adopt Example Queue"                    # creates docs/plans/<id>.md
+docs check [--root DIR]                                # prints path:line: message; exit 1 on problems
+```
+
+The format is specified in [docs/docs-format.md](docs/docs-format.md); that document is the complete rule set. Exit status is `0` when every record is valid, `1` when problems are reported and `2` for usage errors.
+
+## Status
+
+No support is guaranteed. Breaking changes, including to the format rules, may happen before 1.0 and are listed in the release notes.
+
+## License
+
+BSD-3-Clause, see [LICENSE](LICENSE).