feat: unify source and skills for Dever 0.1.2 installation

.trellis/tasks/10-05-install-entry/implement.jsonl

@@ -0,0 +1,3 @@
+{"file":".trellis/spec/backend/index.md","reason":"Rust compiler scope and checklist"}
+{"file":".trellis/spec/backend/toolchain-and-library.md","reason":"Signed distribution, bootstrap and single ownership"}
+{"file":".trellis/spec/backend/quality-guidelines.md","reason":"Focused offline testing and temporary ownership"}