godot-ts generate crash with GDScript files that have no parsed functions

Hi! I'm using `@godot-js/godot-ts` in a Godot 4.5.1 project and ran into an issue after installing the Terrainy addon from the Godot Asset Library.

Environment:

- Godot 4.5.1 stable
- Windows
- Node v23.7.0
- `@godot-js/godot-ts@0.0.8`
- Package manager: pnpm
- Project also contains GDScript addon files from Terrainy

### What happened

Running:

```text
pnpm run generate
```

with:

```json
"generate": "godot-ts generate"
```

failed with:

```text
TypeError: e.functions is not iterable
at Q (.../@godot-js/godot-ts/dist/index.js:20:45)
at Command.ot (.../@godot-js/godot-ts/dist/index.js:133:232)
```

From debugging, it looks like `godot-ts generate` scans every `.gd` file, creates a descriptor for each one, and then assumes each descriptor has a `functions` array. Some valid GDScript files do not produce any parsed functions, so `functions` is undefined and generation crashes.

The relevant generated code path appears to be equivalent to:

```js
for (let { name, returnType, params } of e.functions) {
// ...
}
```

### Expected behavior

`godot-ts generate` should handle GDScript descriptors with no functions, probably by treating missing `functions` as an empty array.

Something like:

```js
for (let { name, returnType, params } of e.functions ?? []) {
// ...
}
```

### Local workaround

I worked around this by replacing the generator step with a small local script that:

- scans `.gd` files
- always initializes `functions: []`
- writes the same generated `gdscript.d.ts`, `gdscript.ts`, and `utils.ts` files
- compiles the generated helper TypeScript files into:
- `.godot/GodotJS/generated/gdscript.js`
- `.godot/GodotJS/generated/utils.js`

The final compile step was needed because GodotJS reported:

```text
[jsb][Error] the javascript file is missing: res://.godot/GodotJS/generated/gdscript.js (source: res://generated/gdscript.ts)
[jsb][Error] the javascript file is missing: res://.godot/GodotJS/generated/utils.js (source: res://generated/utils.ts)
```

### Related build issue

My original `godot-ts` config used:

```json
"godot-ts": {
"src": ".",
"out": "./.godot/GodotJS",
"minifyClasses": true
}
```

After adding a larger addon and generated files, `godot-ts build` started producing very noisy esbuild out-of-memory failures. Narrowing the script source directory fixed that for my project:

```json
"godot-ts": {
"src": "./src/scripts",
"out": "./.godot/GodotJS/src/scripts",
"minifyClasses": true
}
```

I also ended up using a small local esbuild wrapper for build/watch so only real game TypeScript files under `src/scripts` are compiled.

This may just be a documentation/default-project-layout issue, but it might be worth warning users that `src: "."` can become expensive or unstable once a Godot project contains addon files, generated files, tests, typings, or other non-game TypeScript.

Thanks for the project, it's really nice to be using TypeScript for game dev. Happy to share the workaround script if that helps.