Add Good Dog Rule to AGENTS.md: one integration test per branch, one test per PR

AGENTS.md

@@ -3,6 +3,28 @@
 This file is auto-read at the start of every session. The project keeps its
 memory as a linked map of markdown files — read it before doing anything.
 
+## ⚠️ CRITICAL: The Good Dog Rule
+
+BEFORE any planning or coding, follow this rule:
+
+> ONE integration test per branch, ONE test per PR.
+
+When the user asks for changes that would involve multiple integration tests:
+1. Identify the ONE specific use case/test they want to work on
+2. Do NOT create branches or PRs for multiple tests
+3. Focus ONLY on the single use case until it's complete and tests pass
+
+> *A good dog learns one trick perfectly before learning the next.*
+>
+> PRs that address multiple integration tests will be REJECTED.
+
+MUST read the architecture guide before planning or modifying the codebase:
+[`ai.md`](ai.md) (+ [`schema.md`](schema.md) for the memory-map conventions).
+
+MUST read the coding guide before writing tests or code: the [Working
+rules](#working-rules) in this file — this repo has no `CODING.md`;
+conventions live here and in `ai.md`.
+
 ## Onboarding (in order)
 
 1. [`schema.md`](schema.md) — the memory-map conventions (what lives where, how to keep it true).