[native_doc_dartifier] project set-up with an example

[marshelino-maged]

This PR will be based on PR #2370
closes #2306

• Adding initial translate prompt with its parsing function with the help of JSON schema.
  The prompt contains the information given in the two files https://github.com/dart-lang/native/blob/main/pkgs/jnigen/doc/interface_implementation.md and https://github.com/dart-lang/native/blob/main/pkgs/jnigen/doc/java_differences.md ... I wrote the prompt, then let Gemini refine it.

• Adding the google_generative_ai package to call the LLM.

• Adding an example usage of the current set-up.

---

• I’ve reviewed the contributor guide and applied the relevant portions to this PR.

[github-actions]

PR Health

Changelog Entry ❗

Package	Changed Files
package:native_doc_dartifier	pkgs/native_doc_dartifier/lib/src/ast.dart pkgs/native_doc_dartifier/lib/src/dartify_code.dart pkgs/native_doc_dartifier/lib/src/prompts.dart pkgs/native_doc_dartifier/pubspec.yaml

Changes to files need to be accounted for in their respective changelogs.

This check can be disabled by tagging the PR with skip-changelog-check.

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbols

License Headers ✔️

// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

Files
no missing headers

All source files should start with a license header.

Unrelated files missing license headers

Files
pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/native_doc_dartifier/lib/native_doc_dartifier.dart
pkgs/native_doc_dartifier/lib/src/native_doc_dartifier_base.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[HosseinYousefi]

You need to change the CI to use Flutter because package:jni still uses Flutter plugin system so you'd need to run flutter pub get instead. I'll merge it once you change this.

[HosseinYousefi]

LGTM!