fix(brew search): Improve hints for apps migrated within the same tap

[yermulnik]

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Since the #21224 was merged and released via https://github.com/Homebrew/brew/releases/tag/5.0.6, the tap migrations within the same tap are working for the third-party taps. However the same wasn't implemented for brew search which still outputs odd hints for such apps that were migrated from a formula to a cask within the same tap. E.g.:

> brew search tfswitch
[…]
==> Casks
yermulnik/tfswitch-homebrew-tap/tfswitch

If you meant "tfswitch" specifically:
It was migrated from yermulnik/tfswitch-homebrew-tap to tfswitch.
You can access it again by running:
  brew tap tfswitch/
And then you can install it by running:
  brew install tfswitch

This is a follow up to #21207 and attempts to provide a more meaningful and correct hints for apps migrated within the same tap.

Cc @MikeMcQuaid

[Copilot]

Pull request overview

This PR updates Homebrew’s missing-formula hinting to produce more accurate guidance when a formula has been migrated to a cask within the same tap, improving the brew search/missing formula messaging for third-party taps using tap_migrations.json.

Changes:

• Add a “same tap” migration path that changes the message and avoids suggesting brew tap … when the migration stays within the same tap.
• Adjust the suggested install command to use brew install --cask for same-tap formula→cask migrations.
• Simplify/reshape the output formatting to better fit the new messaging.

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[MikeMcQuaid]

Thanks for the PR @yermulnik! This logic all looks good and makes sense to me and the wording improvements are 😍.

Just requesting @cho-m give it another look as I'm always a bit twitchy about this sort of logic.