fix(nix): disable pre-commit check in flake check, keep mypy hook

Configure git-hooks to skip the check during 'nix flake check' because
mypy requires the Python environment which isn't available in the Nix
sandbox.

The mypy hook still works locally in 'nix develop' where the Python
environment is available. Mypy is also run in CI via ci.yml.

Changes:
- Set pre-commit.check.enable = false to skip flake check
- Keep mypy hook enabled for local development
- Treefmt check still runs in flake check

Author: ryoppippi

flake.nix

@@ -46,18 +46,21 @@
           };
 
           # Git hooks configuration
-          pre-commit.settings.hooks = {
-            treefmt = {
-              enable = true;
-              package = config.treefmt.build.wrapper;
-            };
-            mypy = {
-              enable = true;
-              name = "mypy";
-              entry = "${pkgs.uv}/bin/uv run mypy";
-              files = "^stackone_ai/";
-              language = "system";
-              types = [ "python" ];
+          pre-commit = {
+            check.enable = false; # Skip check in flake (mypy needs Python env)
+            settings.hooks = {
+              treefmt = {
+                enable = true;
+                package = config.treefmt.build.wrapper;
+              };
+              mypy = {
+                enable = true;
+                name = "mypy";
+                entry = "${pkgs.uv}/bin/uv run mypy";
+                files = "^stackone_ai/";
+                language = "system";
+                types = [ "python" ];
+              };
             };
           };