[hooks] Stop leaking MetadataAsset

[dcharkes]

Also, nest _parseAssets in an extension. The leaking tool seems to think it's exported. So just work around it. (And make the fromSyntax similar to other syntax methods.)

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:code_assets	0.19.4	already published at pub.dev
package:data_assets	0.19.1	already published at pub.dev
package:ffi	2.1.4	already published at pub.dev
package:ffigen	19.1.0-wip	WIP (no publish necessary)
package:hooks	0.19.5	ready to publish	hooks-v0.19.5
package:hooks_runner	0.21.0	already published at pub.dev
package:jni	0.14.2	already published at pub.dev
package:jnigen	0.15.0-wip	WIP (no publish necessary)
package:native_doc_dartifier	0.0.1-pre	already published at pub.dev
package:native_toolchain_c	0.16.3	already published at pub.dev
package:objective_c	8.1.0-wip	WIP (no publish necessary)
package:swift2objc	0.0.1-wip	WIP (no publish necessary)
package:swiftgen	0.0.1-wip	WIP (no publish necessary)

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[github-actions]

PR Health

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/example/native_doc_dartifier_example.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

[auto-submit]

autosubmit label was removed for dart-lang/native/2357, because - The status or check suite health / changelog / run changelog health check has failed. Please fix the issues identified (or deflake) before re-applying this label.

[auto-submit]

autosubmit label was removed for dart-lang/native/2357, because - The status or check suite health / changelog / run changelog health check has failed. Please fix the issues identified (or deflake) before re-applying this label.

[coveralls]

coverage: 88.001%. remained the same
when pulling 32c54ff on leaked-members
into 33c0251 on main.