docs(slice-4): BOOTSTRAP.md PPE runbook, version 0.4.0, README status

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

README.md

@@ -27,5 +27,7 @@ complete entry-routing rule (landing / create-storefront / admin), and the INV-1
 whole-flow bootstrap test — all skinned to the Claude Design export
 (`wiggleverse-ecomm-content/ui/designs/ecomm-login-and-create-storefront-designs/`),
 which also re-skinned the SLICE-2 Landing + Sign-in screens. See
-[`docs/BOOTSTRAP.md`](./docs/BOOTSTRAP.md) to run it locally. Deployed environments
-(SLICE-4) are next.
+[`docs/BOOTSTRAP.md`](./docs/BOOTSTRAP.md) to run it locally. SLICE-4's deploy
+contract is in place (versioned `/healthz`, backend-served SPA, `SmtpMailer` with
+honest 502 on delivery failure); PPE provisioning + the bootstrap rehearsal are the
+remaining SLICE-4 steps (BOOTSTRAP.md's PPE section is the runbook).