docs: require installing test runtimes

Author: henry701

AGENTS.md

@@ -143,6 +143,7 @@ const table = sqliteTable("session", {
 - Avoid mocks as much as possible, you shouldn't be using globalThis.\* at all unless it's the only option.
 - Test actual implementation, do not duplicate logic into tests
 - Tests cannot run from repo root (guard: `do-not-run-tests-from-root`); run from package dirs like `packages/opencode`.
+- When a required test runtime or tool is missing, install it and continue the relevant validation. Do not treat an installable dependency as a blocker.
 
 ## Type Checking