fix(installer): repair git init, LUKS reprompt, impermanence-no exit, quiet disko

- nrun git git init -q passed 'git' as a subcommand to git itself,
  failing the post-disko repo init. Drop the duplicated arg.
- disko's luks module reads passwordFile at the top level; placing it
  under settings.* meant it was silently ignored and disko fell back
  to askPassword=true, prompting the user again on luksOpen. Move the
  option to the right scope.
- configure_impermanence now uses local rc, nrun gum confirm, and an
  explicit case (0/1/130) with a final return 0 so a No answer no
  longer aborts the installer.
- run_disko_with_retry hides disko's chatty output behind a gum spin
  by default and surfaces the captured log on failure. Set
  NOMARCHY_VERBOSE_DISKO=1 to stream output live.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

installer/disko-config.nix

@@ -44,8 +44,8 @@ let
           content = {
             type = "luks";
             name = extraLuks drive;
+            passwordFile = "/dev/shm/nomarchy-luks.key";
             settings.allowDiscards = true;
-            settings.passwordFile = "/dev/shm/nomarchy-luks.key";
             content.type = "btrfs";
           };
         };
@@ -116,8 +116,8 @@ in {
             content = {
               type = "luks";
               name = mainLuksName;
+              passwordFile = "/dev/shm/nomarchy-luks.key";
               settings.allowDiscards = true;
-              settings.passwordFile = "/dev/shm/nomarchy-luks.key";
               content = rootBtrfs;
             };
           };