docs: add agent guidelines and coding conventions

.github/workflows/tests.yml

@@ -6,6 +6,10 @@ on:
     branches:
       - main
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: ${{ matrix.os }}

AGENTS.md

@@ -0,0 +1,11 @@
+# Agent Guidelines
+
+- install: `npm install`
+- test: `npm test`
+- coverage: `npm run coverage`
+
+Release automated by `.github/workflows/release.yml`, do not alter version.
+
+Follow all coding and commit conventions in `CONTRIBUTING.md`.
+
+Omit AI attribution in commits (Co-authored-by). Polluting git history with AI advertising is not allowed.

CLAUDE.md

@@ -0,0 +1 @@
+AGENTS.md

CONTRIBUTING.md

@@ -2,4 +2,27 @@
 
 ## Code of Conduct
 
-This project is intended to be a safe, welcoming space for collaboration. All contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct. Thank you for being kind to each other!
+This project is intended to be a safe, welcoming space for collaboration. All contributors are expected to adhere to the [Contributor Covenant](https://contributor-covenant.org) code of conduct. Thank you for being kind to each other!
+
+## Contributions welcome!
+
+**Before spending lots of time on something, ask for feedback on your idea first!**
+
+Please search [issues](../../issues/) and [pull requests](../../pulls/) before adding something new! This helps avoid duplicating efforts and conversations.
+
+This project welcomes any kind of contribution! Here are a few suggestions:
+
+- **Ideas**: participate in an issue thread or start your own to have your voice heard.
+- **Writing**: contribute your expertise in an area by helping expand the included content.
+- **Copy editing**: fix typos, clarify language, and generally improve the quality of the content.
+- **Formatting**: help keep content easy to read with consistent formatting.
+- **Code**: help maintain and improve the project codebase.
+
+## Coding Guidelines
+
+- Commits should be atomic and adhere to [conventional commit](https://conventionalcommits.org) standards.
+- Commit messages should be short (`<topic>: <action>`, 50 char max), and commit bodies only included when necessary for complex changes (72 char max).
+- Breaking changes are discouraged, and require a `BREAKING CHANGE:` footer in the commit body explaining the change.
+- Types and interfaces should be inlined unless they're absolutely necessary for exporting or testing.
+- Avoid unnecessary code comments, and keep necessary ones trim.
+- All changes should maintain the test coverage gate (100%).