Unify includes and excludes into single ordered pattern list

The file content attachment handler should not separate includes and excludes into separate collections, but instead maintain a single ordered list of patterns where order matters for precedence, similar to how gitignore files work.

Context

Currently, the FileContent struct maintains separate BTreeSet<Pattern> collections for includes and excludes. However, this approach doesn't align with how gitignore patterns work, where the order of patterns matters for precedence.

In gitignore syntax, patterns are evaluated in order, and later patterns can override earlier ones. For example:

• foo/ (exclude all foo directories)
• !foo/important.txt (but include this specific file)

The current approach makes it impossible to have proper precedence because includes and excludes are processed separately, and the CLI argument order (-a one -a two) should be preserved so that two is processed after one.

Proposed Implementation

1. Replace the separate includes and excludes fields with a single patterns: Vec<(Pattern, bool)> where the boolean indicates whether it's an include (true) or exclude (false) pattern.

2. Modify the add method to append patterns to this vector in order, preserving the CLI argument sequence.

3. Update the get method to process patterns in order when building the OverrideBuilder.

4. Update the list method to return patterns in their original order.

5. Update the serialization to preserve order (using Vec instead of BTreeSet).

Resources

• https://github.com/dcdpr/jp/blob/main/crates/jp_attachment_file_content/src/lib.rs#L25-L30
• https://github.com/dcdpr/jp/blob/main/crates/jp_attachment_file_content/src/lib.rs#L38-L51

Start in crates/jp_attachment_file_content/src/lib.rs, especially the FileContent fields and its add, get, and list methods. Trace how OverrideBuilder and serialization use the patterns, then verify that CLI argument order and serialized output preserve precedence and original ordering.