Update instructions for humans and agents

AGENTS.md

@@ -1,6 +1,23 @@
-# ALE Agent instructions
+# ALE Instructions
 
-1. Read documentation from `doc/ale-development.txt` to understand how to be an
-   ALE developer.
-2. Run Vader/Vim tests with `./run-tests -q --fast test/path/some_file.vader`
-3. When editing Lua code run Lua tests with `./run-tests -q --lua-only`
+## Basic Instructions
+
+Read documentation from @doc/ale-development.txt to understand how to be an
+ALE developer and how to match our standards.
+
+Run all tests quickly with `./run-tests -q --fast`, which picks the quickest
+version of Neovim we can run, and runs our linting checks.
+
+You can quickly check an individual Vader test file by passing them as arguments
+such as `./run-tests -q --fast test/path/some_file.vader`.
+
+You can quickly run all Lua tests with `./run-tests -q --lua-only`.
+
+
+For new Vim files, set `Author:` comments to the person doing the work.
+Do not use Codex, OpenAI, or other tool names as the author.
+
+## Writing Tests
+
+For `test/test-files` they should almost always be 0 bytes in size and files
+may be marked executable when testing searching for executables.