pinwheel: Make claude settings writable with nix as defaults

hosts/pinwheel/modules/ai/default.nix

@@ -47,6 +47,8 @@ let
       ];
     };
   };
+
+  settingsFile = pkgs.writeText "claude-settings.json" settings;
 in
 {
   options = {
@@ -68,8 +70,18 @@ in
           pclaude = "CLAUDE_CONFIG_DIR=$HOME/.claude-personal command claude";
         };
 
-        home.file.".claude-work/settings.json".text = settings;
-        home.file.".claude-personal/settings.json".text = settings;
+        home.activation.claudeSettings = {
+          after = [ "linkGeneration" ];
+          before = [ ];
+          data = ''
+            for f in "$HOME"/.claude-{work,personal}/settings.json; do
+              current="$(cat "$f" 2>/dev/null || echo '{}')"
+              run mkdir -p "$(dirname "$f")"
+              run rm -f "$f"
+              echo "$current" | ${pkgs.jq}/bin/jq -s '.[0] * .[1]' ${settingsFile} - | run tee "$f" > /dev/null
+            done
+          '';
+        };
 
         programs.ct = {
           enable = true;