chore: unbundled ISO builds on main, full Debian ISO manual-only

- build-iso-dev.yml now triggers on both main and dev-iso
- build-iso.yml (full Debian) is workflow_dispatch only

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-iso-dev.yml

@@ -2,7 +2,7 @@ name: Build Archipelago ISO (dev)
 
 on:
   push:
-    branches: [dev-iso]
+    branches: [main, dev-iso]
   workflow_dispatch:
 
 jobs:

.gitea/workflows/build-iso.yml

@@ -1,8 +1,6 @@
 name: Build Archipelago ISO
 
 on:
-  push:
-    branches: [main]
   workflow_dispatch:
 
 jobs: