docs: record that merging to main promotes production

docs/superpowers/plans/2026-09-02-growth-hard-cutover.md

@@ -994,6 +994,12 @@ Deploy the merged commit, verify unauthenticated rejection and authenticated rea
 
 - [ ] **Step 6: Prepare—but do not promote—the website deployment**
 
+> **This step is not achievable on this project and was never verified before it was written.** The `threadplane` Vercel project promotes every `main` deployment automatically; `main` is the only branch that has ever reached production, across at least the last 40 production deployments. Merging the cutover pull request therefore *is* the promotion, and it happened seconds after #968 merged on 2026-09-03, before any firewall block, drain, snapshot, import, or cancellation had run.
+>
+> Task 11's ordering depends on the same false assumption: it blocks form ingress, reconciles the legacy provider state, and only then promotes the hard boundary. On this project the boundary is already live the moment the code lands.
+>
+> Any future cutover of this shape must either disable automatic production promotion on the project first, or be re-sequenced so the legacy provider inventory is imported and cancelled **before** the code merges.
+
 Build/deploy the merged website artifact with `growth_v1`. Verify configuration, database reachability, lifecycle reachability, and bundle absence of legacy code on its deployment URL. Do not route production form traffic to it yet.
 
 - [x] **Step 7: Prepare and verify the rollback control before cutover**
@@ -1043,6 +1049,8 @@ If any condition fails, keep the firewall and all campaign switches off. Follow
 
 - [ ] **Step 6: Promote the hard-boundary website while forms remain blocked**
 
+> Superseded on this project — see the note on Task 10 Step 6. Promotion is automatic on merge, so there is no separate promote to hold until forms are blocked.
+
 Promote the prepared website deployment. Verify production is on the merged commit, `growth_v1` is active, and static/runtime probes find no NDJSON, Loops, Audience, direct send, or provider scheduling path.
 
 - [ ] **Step 7: Reopen forms and capture the immutable cohort instant**

docs/superpowers/runbooks/2026-08-31-growth-lifecycle-cutover.md

@@ -2,6 +2,12 @@
 
 Status: **LOCAL implementation and harness only.** No disposable database, preview, or production action in this runbook has been performed. No Neon migration/import, Resend/Google read or write, Vercel deployment, Dawn deployed request, or switch change is implied by local test results.
 
+## Deployment promotion is automatic
+
+The `threadplane` Vercel project promotes every `main` deployment to production automatically, and `main` is the only branch that has ever reached production. There is no "build but do not promote" state for the website: **merging is promoting.** Sequence any cutover around that, and never write a step that depends on holding a merged commit back from production.
+
+The `threadplane-lifecycle` project behaves the same way on `main`.
+
 ## Gate classes
 
 - **LOCAL**: repository-only and safe with fake fixtures; no provider or database connection.