docs(agent): AGENTS.md explicitly requires reading VERIFICATION.md first

The enforcement rules must not depend on any harness's skill/trigger
mechanism — the auto-loaded entry point itself now instructs every
agent to read agent/VERIFICATION.md before its first change (and
THEME-DESIGN.md / TESTING.md where relevant), instead of merely
pointing at them.

Verification: V0 (docs-only).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

AGENTS.md

@@ -26,6 +26,10 @@ item → work → verify → commit+push on `main` → record. All loop state is
 git-tracked in `agent/`.
 
 ## Rules that apply to every session, loop or not
+- **Before your first change, read `agent/VERIFICATION.md`** and follow
+  it — every change, however small, climbs its V0–V3 ladder. For theme
+  or visual work, also read `agent/THEME-DESIGN.md`; before any VM test,
+  `docs/TESTING.md`.
 - **Honesty rule** (`agent/VERIFICATION.md`, `docs/TESTING.md`): for
   visual/interactive changes, evaluation is not rendering — state the
   tier you reached. Cheap first: `nix flake check --no-build`.