chore: import upstream snapshot with attribution

dev.env.example

@@ -0,0 +1,20 @@
+# Per-developer module-branch selection. Copy to `dev.env` (gitignored) and
+# set the branch(es) you're working on. `make use` checks them out; `make dev`
+# / `make dev-web` (local source) follow them, and `make server` / `make app`
+# install the matching Electron desktop server.
+#
+#   cp dev.env.example dev.env
+#   # edit, then:
+#   make use && make dev          # local-source dev on your branches
+#   # or for the desktop app on your branch's server:
+#   make server && make app
+#
+# Leave unset to track `main`.
+
+# All modules on one branch:
+# REF=feat/my-thing
+
+# …or override per module (these win over REF):
+# FRONTEND_REF=feat/ui-thing
+# API_REF=feat/server-thing
+# AGENT_REF=feat/agent-thing