chore: add gopls LSP configuration for Claude Code

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/gopls-wrapper.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+exec nix develop --quiet -c gopls "$@"

.claude/settings.json

@@ -0,0 +1,10 @@
+{
+  "lspServers": {
+    "gopls": {
+      "command": ".claude/gopls-wrapper.sh",
+      "extensionToLanguage": {
+        ".go": "go"
+      }
+    }
+  }
+}