docs: direct feature work to develop branch in AGENTS.md

AGENTS.md

@@ -24,6 +24,10 @@ Strict one-way MVVM + services: `views → viewmodels → services → core`.
 
 Runner emits OpenSeesPy commands in fixed order (`docs/architecture.md`): `wipe → model → node → fix → material → section → geomTransf → element → timeSeries → pattern/load → recorder → system/numberer/... → analyze`. Never reorder.
 
+## Branches
+
+- Do all feature/fix work on `develop` (or short-lived branches off `develop`, merged back into it). `main` is release-only — never commit directly to it.
+
 ## Verify (in this order)
 
 ```bash