fix: separate ignore instances for .gitignore and .ignore

[brandtcormorant]

What does this PR do?

Fixes #4739

This fixes File.list() to process .gitignore and .ignore separately instead of merging them into a single ignore instance. This allows .ignore negation patterns (e.g. !/foo/) to override .gitignore rules, matching the intended behavior where .ignore controls what tools like the filepicker show independently of what git tracks.

My use case is to ignore git repos inside another git repo but still be able to traverse them in the filepicker.

An example of what this pull request enables:

.gitignore:

/repositories/*

.ignore:

!/repositories/
!/repositories/**
/repositories/**/.git/
/repositories/**/node_modules/

This is useful in a workspace that isn't a monorepo but that manages a set of repositories. There are probably other use cases for the changes in this pull request, things like having gitignored sandbox or tmp directories where we still want to easily reference the contents.

How did you verify your code works?

Ran tests to make sure nothing broke and launched using bun dev path/to/project/ where i had .gitignore and .ignore files set up like above.

[github-actions]

Hey! Your PR title use separate ignore instances for .gitignore and .ignore doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.