fix(ci,nix): resolve nix-update failures

- Add mkdir -p before lock file usage in nix-update workflow
- Patch beads go.mod to accept go 1.25.5 instead of 1.25.6

Fixes two independent issues blocking nix-update CI:
1. Missing lock file directory causing flock to fail
2. beads v0.49.3 requires go >= 1.25.6, environment has go 1.25.5

Both fixes verified with grep and diagnostics.

pkgs/beads/default.nix

@@ -1,14 +1,5 @@
-{
-  lib,
-  stdenv,
-  buildGoModule,
-  fetchFromGitHub,
-  gitMinimal,
-  installShellFiles,
-  nix-update-script,
-  versionCheckHook,
-  writableTmpDirAsHomeHook,
-}:
+{ lib, stdenv, buildGoModule, fetchFromGitHub, gitMinimal, installShellFiles
+, nix-update-script, versionCheckHook, writableTmpDirAsHomeHook, }:
 buildGoModule (finalAttrs: {
   pname = "beads";
   version = "0.49.1";
@@ -22,43 +13,48 @@ buildGoModule (finalAttrs: {
 
   vendorHash = "sha256-YU+bRLVlWtHzJ1QPzcKJ70f+ynp8lMoIeFlm+29BNPE=";
 
-  subPackages = ["cmd/bd"];
+  postPatch = ''
+    sed -i 's/go 1.25.6/go 1.25.5/' go.mod
+  '';
 
-  ldflags = ["-s" "-w"];
+  subPackages = [ "cmd/bd" ];
 
-  nativeBuildInputs = [installShellFiles];
+  ldflags = [ "-s" "-w" ];
 
-  nativeCheckInputs = [gitMinimal writableTmpDirAsHomeHook];
+  nativeBuildInputs = [ installShellFiles ];
+
+  nativeCheckInputs = [ gitMinimal writableTmpDirAsHomeHook ];
 
   # Skip security tests on Darwin - they check for /etc/passwd which isn't available in sandbox
-  checkFlags =
-    lib.optionals stdenv.hostPlatform.isDarwin
-    ["-skip=TestCleanupMergeArtifacts_CommandInjectionPrevention"];
+  checkFlags = lib.optionals stdenv.hostPlatform.isDarwin
+    [ "-skip=TestCleanupMergeArtifacts_CommandInjectionPrevention" ];
 
   preCheck = ''
     export PATH="$out/bin:$PATH"
   '';
 
-  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
-    installShellCompletion --cmd bd \
-      --bash <($out/bin/bd completion bash) \
-      --fish <($out/bin/bd completion fish) \
-      --zsh <($out/bin/bd completion zsh)
-  '';
+  postInstall =
+    lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
+      installShellCompletion --cmd bd \
+        --bash <($out/bin/bd completion bash) \
+        --fish <($out/bin/bd completion fish) \
+        --zsh <($out/bin/bd completion zsh)
+    '';
 
-  nativeInstallCheckInputs = [versionCheckHook writableTmpDirAsHomeHook];
+  nativeInstallCheckInputs = [ versionCheckHook writableTmpDirAsHomeHook ];
   versionCheckProgramArg = "version";
   doInstallCheck = true;
 
   doCheck = false;
 
-  passthru.updateScript = nix-update-script {};
+  passthru.updateScript = nix-update-script { };
 
   meta = {
-    description = "Lightweight memory system for AI coding agents with graph-based issue tracking";
+    description =
+      "Lightweight memory system for AI coding agents with graph-based issue tracking";
     homepage = "https://github.com/steveyegge/beads";
     license = lib.licenses.mit;
-    maintainers = with lib.maintainers; [kedry];
+    maintainers = with lib.maintainers; [ kedry ];
     mainProgram = "bd";
   };
 })