[tool] Enforce README package table order

[faheemabbas766]

Adds repository-info validation that rejects package rows in the root README when they are not sorted alphabetically. The error identifies the first out-of-order pair.

This also adds regression coverage and sorts the three existing out-of-order rows so the repository passes the new validation.

Fixes flutter/flutter#188727.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

The tool already has a NEXT CHANGELOG section, so this change adds its release note there without changing the package version.

Validation:

• dart format --output=none --set-exit-if-changed lib/src/validators/repo_info_validator.dart test/validate_command_repo_info_test.dart
• dart analyze --fatal-infos
• dart test test/validate_command_repo_info_test.dart (29 tests)
• dart test (1,221 tests)

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Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

[gemini-code-assist]

Code Review

This pull request adds validation to ensure that the package table in the root README.md is sorted alphabetically. It updates RepoInfoValidator to track the alphabetical order of entries, introduces a new exit code for unsorted tables, and adds a corresponding unit test to verify this behavior. The root README.md table is also updated to be sorted alphabetically. There are no review comments, so no additional feedback is provided.