feat: add nixd option completion, just-lsp config, and vscode nix settings

.gitignore

@@ -1,5 +1,6 @@
 result
 .direnv
+.nixd.json
 
 # Never commit plaintext secrets
 *.dec.yaml

.vscode/settings.json

@@ -0,0 +1,14 @@
+{
+	"nix.enableLanguageServer": true,
+	"nix.serverPath": "nixd",
+	"nix.serverSettings": {
+		"nixd": {
+			"formatting": {
+				"command": ["nixfmt"]
+			},
+			"nixpkgs": {
+				"expr": "import <nixpkgs> {}"
+			}
+		}
+	}
+}

Justfile

@@ -37,3 +37,14 @@ check:
 [linux]
 check:
     @nix eval .#nixosConfigurations.wsl.config.system.build.toplevel > /dev/null && echo "wsl: ok"
+
+# Generate .nixd.json for nixd LSP option completion
+[macos]
+nixd host:
+    @echo '{"options":{"nix-darwin":{"expr":"(builtins.getFlake (toString ./.)).darwinConfigurations.{{host}}.options"},"home-manager":{"expr":"(builtins.getFlake (toString ./.)).darwinConfigurations.{{host}}.options.home-manager.users.type.getSubOptions []"}}}' | jq . > .nixd.json
+    @echo "Generated .nixd.json for {{host}}"
+
+[linux]
+nixd host="wsl":
+    @echo '{"options":{"nixos":{"expr":"(builtins.getFlake (toString ./.)).nixosConfigurations.{{host}}.options"},"home-manager":{"expr":"(builtins.getFlake (toString ./.)).nixosConfigurations.{{host}}.options.home-manager.users.type.getSubOptions []"}}}' | jq . > .nixd.json
+    @echo "Generated .nixd.json for {{host}}"

opencode.jsonc

@@ -1,5 +1,11 @@
 {
 	"$schema": "https://opencode.ai/config.json",
+	"lsp": {
+		"just": {
+			"command": ["just-lsp"],
+			"extensions": [""]
+		}
+	},
 	"mcp": {
 		"nixos": {
 			"type": "local",