install tools on devcontainer creation

this will stop vscode's Go extension of installing `golangci-lint@latest`

.devcontainer/devcontainer.json

@@ -12,7 +12,7 @@
   "remoteUser": "vscode",
 
   // Run once after the container is created.
-  "postCreateCommand": "make init",
+  "postCreateCommand": "make init && make tools",
 
   // Fix ownership of the mounted ~/.claude so the vscode user can read host auth.
   "postStartCommand": "sudo chown -R vscode:vscode /home/vscode/.claude 2>/dev/null || true",
@@ -35,6 +35,7 @@
         "github.copilot.inlineSuggest.enable": false,
 
         "go.useLanguageServer": true,
+        "go.toolsManagement.autoUpdate": false,
         "go.lintTool": "golangci-lint",
         "go.lintFlags": ["--fast"],
         "go.lintOnSave": "workspace",