feat: Update documentation to clarify Nix usage and enhance onboarding for non-Nix contributors

flake.nix

@@ -36,7 +36,7 @@
       templates = {
         default = {
           path = ./.;
-          description = "FeDIY Rust development environment and package outputs for Nix and non-Nix contributors";
+          description = "FeDIY Rust development environment and package outputs; Nix is optional for contributors";
         };
       };
 
@@ -106,8 +106,8 @@
               fi
 
               echo "[FeDIY] Welcome to the dev shell!"
-              echo "If you're new to Nix: this shell gives you the exact tools this repo expects."
-              echo "Start with 'cargo build'. Use 'nix run .#dev-helper' for a quick tool summary."
+              echo "Nix is optional for contributors. This shell is here if you want a ready-made toolset."
+              echo "Start with 'cargo build'. Use 'nix run .#dev-helper' for a quick task summary."
               echo "Tools: cargo, rustc, clippy, rustfmt, rust-analyzer, flatpak-builder, psql, gettext, chromium, playwright"
               echo "Packaging note: the shell is intentionally reviewed and trimmed as the roadmap changes."
               if command -v podman >/dev/null 2>&1; then