fix(nix): use same nodejs version everywhere & small lints

- prevent lockfile thrashing while using nix :3
- use lib.getExe instead of raw /bin/ paths
- use inputs'.self instead of passing system in manually

nix/devShell.nix

@@ -1,29 +1,30 @@
 # nix/devShell.nix — Dev shell that delegates setup to each package
 #
-# Each package in inputsFrom exposes passthru.devShellHook — a bash snippet
+# Each package in inputsFrom might expose passthru.devShellHook — a bash snippet
 # with stamp-checked setup logic. This file collects and runs them all.
-{ inputs, ... }: {
-  perSystem = { pkgs, system, ... }:
+{ ... }:
+{
+  perSystem =
+    { pkgs, self', ... }:
     let
-      hermes-agent = inputs.self.packages.${system}.default;
-      hermes-tui = inputs.self.packages.${system}.tui;
-      hermes-web = inputs.self.packages.${system}.web;
-      packages = [ hermes-agent hermes-tui hermes-web ];
-    in {
+      packages = builtins.attrValues self'.packages;
+    in
+    {
       devShells.default = pkgs.mkShell {
         inputsFrom = packages;
         packages = with pkgs; [
-          python312 uv nodejs_22 ripgrep git openssh ffmpeg
+          uv
         ];
-
-        shellHook = let
-          hooks = map (p: p.passthru.devShellHook or "") packages;
-          combined = pkgs.lib.concatStringsSep "\n" (builtins.filter (h: h != "") hooks);
-        in ''
-          echo "Hermes Agent dev shell"
-          ${combined}
-          echo "Ready. Run 'hermes' to start."
-        '';
+        shellHook =
+          let
+            hooks = map (p: p.passthru.devShellHook or "") packages;
+            combined = pkgs.lib.concatStringsSep "\n" (builtins.filter (h: h != "") hooks);
+          in
+          ''
+            echo "Hermes Agent dev shell"
+            ${combined}
+            echo "Ready. Run 'hermes' to start."
+          '';
       };
     };
 }