chore: add deno.json for editor IntelliSense and update README

README.md

@@ -23,4 +23,19 @@ Functions prefixed with `API_` are auto-routed:
 
 ## Environment Variables
 
-- `GREETING_PREFIX` — custom greeting prefix (default: "Hello")
+- `GREETING_PREFIX` — custom greeting prefix (default: "Hello")
+
+## Editor Setup
+
+The `pages/` folder contains a `deno.json` so Deno-aware editors pick up the
+correct globals (`Deno.env`, `Deno.serve`, etc.).
+
+**VS Code:** install the
+[Deno extension](https://marketplace.visualstudio.com/items?itemName=denoland.vscode-deno)
+and enable it for the `pages/` folder (it should pick up `deno.json`
+automatically).
+
+**JetBrains IDEs:** the built-in Deno plugin works the same way.
+
+Without a Deno-aware editor, `Deno.env` will show as an undefined identifier
+— but the code still runs correctly inside the generated container.