[Experiment DNM] Adds Gemini CLI to Github Actions

[ericwindmill]

Pre-launch Checklist

• I read the [Flutter Style Guide] recently, and have followed its advice.
• I signed the [CLA].
• I read the [Contributors Guide].
• I have added sample code updates to the [changelog].
• I updated/added relevant documentation (doc comments with ///).

[github-actions]

📋 Review Summary

This PR introduces a comprehensive set of GitHub Actions workflows powered by the Gemini CLI to automate various repository management tasks, including PR reviews, issue triage, and general assistance. The workflows are well-structured and the prompts are detailed, which is great.

🔍 General Feedback

• The workflows are very powerful and will be a great addition to the repository.
• The prompts for the Gemini CLI are well-written and provide clear instructions.
• I've made a few suggestions to improve the readability and maintainability of the workflow files, mainly by simplifying conditions and commands.
• I've also pointed out a few potential issues in the prompt files that could be improved.
• There is one unrelated change in a pubspec.yaml file that seems to be a mistake.

Overall, this is a great PR that will significantly improve the automation of this repository.

[github-actions]

🟡 This condition is very complex and repeated across multiple workflows. To improve readability and maintainability, you can use the contains function to simplify the author association check.

Suggested change

	github.event.sender.type == 'User' && (
	(
	github.event.sender.type == 'User' &&
	contains(['OWNER', 'MEMBER', 'COLLABORATOR'], github.event.issue.author_association)
	)

This can be applied to all the author association checks in this file.

[github-actions]

🟡 You can use the contains function to simplify the author association check, making the condition more readable and maintainable.

Suggested change

	github.event.comment.author_association == 'MEMBER' ||
	(github.event_name == 'issue_comment' &&
	contains(github.event.comment.body, '@gemini-cli /triage') &&
	contains(['OWNER', 'MEMBER', 'COLLABORATOR'], github.event.comment.author_association))

[github-actions]

🟡 The git command for finding the most recent commit might not be compatible with all git versions due to the negative lookahead in the author filter. A more compatible way to exclude bots is to use --invert-grep. Also, the path globbing might not work as expected. It's better to run the command from the project root and specify the path.

Suggested change

	```bash
	git log -1 --author='bot' --invert-grep --pretty="format:%ad" --date=short -- path/to/project/**/*.dart

You would need to replace path/to/project with the actual path to the project. Or, if running from the project directory, just use . as the path.

git log -1 --author='bot' --invert-grep --pretty="format:%ad" --date=short -- .

[github-actions]

🟡 This change downgrades the SDK constraint. Given the PR title, this seems unrelated and might be an accidental change. Please verify if this downgrade is intended.