Migration tool interactive mode updates

[aemous]

Description of changes:

• Deleted modeled suggested_manual_fix property from LintFinding, and removed the property from all classes that specified one. This change is based on feedback that the manual-review findings were too verbose.
• Added two new options to interactive mode: accept all of type and reject all of type, which accepts and rejects all remaining findings for the displayed rule, respectively.
• Added 5 new tests for interactive mode for the two new options.
• Replace use of | with │ for the margin when displaying diffs, for an improved appearance.
• Improved spacing between findings in interactive mode, and before the first finding in dry-run mode and auto-fix mode.
• Upgraded the version of ast-grep-py dependency to 0.40.5.
• Removed contribution guidelines from the README and moved it to a new file CONTRIBUTING.md.
• Added new "Supported Breaking Changes" and "Backwards Compatibility Policy" sections to the README.
• Updated tests based on the changes above.
• Updated the uv.lock file based on automatically generated changes.

Description of tests:

• Successfully ran and passed all tests and linters.
• Manually tested the migration tool across all modes using the example script, and observed expected behavior.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[kdaily]

Looks good overall!

Minor comments:

Some of the added printing/formatting is a bit awkward, going inside some of the higher level methods that apply fixes, instead of being inside display/print methods. Consider if there's a way to move the formatting logic inside for easier focus. Wouldn't block it for that though.

[aemous]

Some of the added printing/formatting is a bit awkward, going inside some of the higher level methods that apply fixes, instead of being inside display/print methods. Consider if there's a way to move the formatting logic inside for easier focus. Wouldn't block it for that though.

I have refactored auto-fix and dry-run modes so that they do not interleave prints with script updates. Now, it collects all the findings while updating the script, and then it prints all the findings and results at the end. This separates printing from core logic.

[kdaily]

Just want to confirm that the intention to have the base64-binary-format and no-cli-pager as interactive fixes from separate discussions matches the implementation here. If I run in non-interactive mode (e.g., --fix) then changes for these rules are applied everywhere.

Other than that, this looks fine and tests locally as expected.