#474: anchor repository mask regex

[akmhatey-ai]

Fixes #474.

What changed:

• Anchor Fbe.mask_to_regex with \A and \z so masks must match the complete org/repo full name.
• Add regression coverage for an exact mask not matching prefix-collision repositories.
• Keep wildcard masks working for normal repository-name suffixes.

Validation:

• Red before implementation: bundle exec ruby test\fbe\test_unmask_repos.rb -- --no-cov failed on the new prefix-collision assertions.
• Green after implementation: bundle exec ruby test\fbe\test_unmask_repos.rb -- --no-cov passed: 7 tests, 18 assertions, 0 failures, 0 errors, 1 skipped.
• bundle exec rubocop lib\fbe\unmask_repos.rb test\fbe\test_unmask_repos.rb passed with no offenses.
• ruby -c lib\fbe\unmask_repos.rb and ruby -c test\fbe\test_unmask_repos.rb passed.
• git diff --check passed.
• git diff -- lib\fbe\unmask_repos.rb test\fbe\test_unmask_repos.rb | gitleaks stdin --no-banner --redact reported no leaks.

Limitation:

• bundle exec rake test is locally blocked on this Windows setup before reaching this patch area because typhoeus/ethon cannot load libcurl while loading unrelated test_enter.rb. I did not change that path.

[GHX5T-SOL]

Verified the mask anchoring change for #474. Anchoring Fbe.mask_to_regex with \A/\z fixes prefix-collision rejects while preserving wildcard suffix matching.

Validation:

• env BUNDLE_PATH=/private/tmp/bundle-fbe-488 mise x ruby@3.3.11 -- bundle check -> dependencies satisfied
• env BUNDLE_PATH=/private/tmp/bundle-fbe-488 mise x ruby@3.3.11 -- bundle exec ruby -Itest test/fbe/test_unmask_repos.rb -- --no-cov -> 7 tests, 18 assertions, 0 failures, 0 errors, 1 skip
• env BUNDLE_PATH=/private/tmp/bundle-fbe-488 mise x ruby@3.3.11 -- bundle exec rake test -> 285 tests, 812 assertions, 0 failures, 0 errors, 9 skips
• env BUNDLE_PATH=/private/tmp/bundle-fbe-488 mise x ruby@3.3.11 -- bundle exec rubocop lib/fbe/unmask_repos.rb test/fbe/test_unmask_repos.rb --format simple -> 2 files inspected, no offenses
• ruby -c lib/fbe/unmask_repos.rb and ruby -c test/fbe/test_unmask_repos.rb -> Syntax OK
• git diff --check origin/master...HEAD -> passed
• git diff origin/master...HEAD | gitleaks stdin --no-banner --redact --exit-code 1 -> no leaks found

Live pre-review state: open, non-draft, mergeable/CLEAN, all GitHub checks green, no existing comments/reviews. Same-scope open PR search for #474 returned only this PR.

[0crat]

@GHX5T-SOL Great work on the review! 🎉 You've earned +6 points (+18 base, -8 for missing comments, -4 for low code coverage with 19 hits). Your total score is now +162 - keep up the momentum and check your Zerocracy account for updates!

[yegor256]

@akmhatey-ai merge conflicts here

[yegor256]

Please fix the merge conflicts so this pull request can be merged.