[friction] ignore bin

[pq]

Agents love to create stuff in bin which we have to manually ignore. The right thing to do is to git ignore the directory.

---

Review the contribution guidelines below:

• I’ve reviewed the contributor guide and applied the relevant portions to this PR.
• I've included the required information in the description above.
• My up-to-date information is in the AUTHORS file.
• I've updated CHANGELOG.md if appropriate.

Contribution guidelines:

• See
  our contributor guide and
  the Flutter organization contributor guide
  for general expectations for PRs.
• Larger or significant changes should be discussed in an issue before creating a PR.
• Dart contributions to our repos should follow the Dart style guide and use
  dart format.
• Java and Kotlin contributions should strive to follow Java and Kotlin best
  practices (discussion).

[gemini-code-assist]

Code Review

This pull request adds the bin/ directory to the .gitignore file. A review comment suggests using the root-relative path /bin/ instead to avoid unintentionally ignoring legitimate Dart source files located in subdirectories, which is a common structure in Flutter projects.