Move ignore into the gitignore module

[UnstoppableMango]

• Remove ignore deps
• New ignore module
• Rename to gitignore
• Gitignore module and filter refactoring
• Tweaks

[Copilot]

Pull request overview

This PR refactors the ignore functionality by extracting gitignore-specific logic into a new dedicated gitignore module, while simplifying the ignore module and enhancing the filter module with more flexible APIs. The changes also include dependency updates and build configuration adjustments.

Key Changes:

• Created a new gitignore module with gitignore-specific functions (moved from ignore module)
• Simplified the ignore module to a minimal generic interface with a single NewFs function
• Refactored the filter module to support both Filter (error-returning) and Predicate (boolean) patterns
• Removed the github.com/sabhiram/go-gitignore dependency from the root module (now only in gitignore)
• Updated various dependencies including golang.org/x tooling

Reviewed changes

Copilot reviewed 21 out of 26 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
gitignore/fs.go	New module containing gitignore-specific filesystem filtering functions
gitignore/fs_test.go	Test suite for the new gitignore module
gitignore/go.mod	Go module definition for the gitignore submodule
ignore/fs.go	Simplified to a minimal generic ignore interface
ignore/fs_test.go	Restructured tests with nested contexts for better organization
filter/fs.go	Enhanced with Filter and Predicate types, added FromFilter and FromPredicate constructors
filter/file.go	Updated to use the new Filter type instead of Predicate
filter/fs_test.go	Restructured tests with nested contexts for better organization
go.mod	Removed gitignore dependency (moved to gitignore submodule)
Makefile	Updated to include gitignore module in build targets
flake.nix	Added gitignore module to Nix flake inputs
gomod2nix.toml, go.sum	Dependency updates and removals

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

❌ Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 62.38%. Comparing base (1f846b0) to head (eba8852).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
filter/fs.go	93.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #108      +/-   ##
==========================================
- Coverage   62.69%   62.38%   -0.31%     
==========================================
  Files          22       22              
  Lines         571      561      -10     
==========================================
- Hits          358      350       -8     
+ Misses        186      185       -1     
+ Partials       27       26       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.