consistently use tarball urls in documentation

otherwise users not using our templates will find themselves missing
git.

docs/site/guides/getting-started/create-installer.md

@@ -55,7 +55,7 @@ sudo umount /dev/sdb1
     - Set your preferred language and keymap
 
     ```bash
-    clan flash write --flake git+https://git.clan.lol/clan/clan-core \
+    clan flash write --flake https://git.clan.lol/clan/clan-core/archive/main.tar.gz \
       --ssh-pubkey $HOME/.ssh/id_ed25519.pub \
       --keymap us \
       --language en_US.UTF-8 \

docs/site/guides/getting-started/index.md

@@ -41,7 +41,7 @@ By the end of this guide, you'll have a fresh NixOS configuration ready to push
 Create a new clan
 
 ```bash
-nix run git+https://git.clan.lol/clan/clan-core#clan-cli --refresh -- flakes create
+nix run https://git.clan.lol/clan/clan-core/archive/main.tar.gz#clan-cli --refresh -- flakes create
 ```
 
 This should prompt for a *name*: