refactor: fix yolo config drift and restart traps

yolo's .claude/settings.json was a full fork of the common file, not the
narrow override its comment claimed: sandbox, defaultMode, voiceEnabled,
$schema and feedbackSurveyState were absent, and five more keys had
diverged. It now holds only yolo's overrides and merges over common via
recursiveUpdate. sandbox.enabled stays pinned false — inheriting it would
newly sandbox every Bash call on a box built for unattended agents.

mutableFiles maps a source back to a repo path for the "bring changes
upstream" hint, which only works inside the flake tree. Generated sources
would print a /nix/store path to copy onto, so add upstreamPath.

rev and rev-deploy set Restart=always with RestartSec=2, which burns
systemd's default 5-starts-per-10s budget and parks the unit in `failed`
until a manual reset-failed. StartLimitIntervalSec=0 lifts the cap.

programs.nh.flake and home.mutableFilesRepoPath become mkDefault so yolo
overrides them plainly instead of with mkForce in three places.

Also clears the outstanding nixfmt and statix findings. The yolo system
derivation hash is unchanged.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

home/common/features/mutable-file.nix

@@ -19,7 +19,11 @@ let
     let
       target = "${config.home.homeDirectory}/${name}";
       storePath = value.source;
-      originalPath = toRepoPath value.source;
+      # toRepoPath only works for sources that live in the flake tree. A
+      # generated source is not under flakePrefix, so removePrefix is a no-op
+      # and the hint would print a /nix/store path to copy back onto.
+      originalPath =
+        if value.upstreamPath != null then "${repoPath}/${value.upstreamPath}" else toRepoPath value.source;
     in
     ''
       if [ -f "${target}" ] && ! ${lib.getExe' pkgs.diffutils "diff"} -q "${storePath}" "${target}" > /dev/null 2>&1; then
@@ -67,6 +71,17 @@ in
             default = false;
             description = "Whether the file should be executable.";
           };
+
+          upstreamPath = lib.mkOption {
+            type = lib.types.nullOr lib.types.str;
+            default = null;
+            example = "home/yolo/claude-settings.json";
+            description = ''
+              Repo-relative file to name in the "bring changes upstream" hint.
+              Required when `source` is generated rather than a file in the
+              flake tree, since the store path cannot be mapped back.
+            '';
+          };
         };
       }
     );