Expose support-bundle parsing through a reusable library crate

Description

Adding a library crate alongside the existing bundle-cat binary would allow other programs to reuse the support-bundle parsing capabilities developed here without invoking the CLI or parsing its formatted output.

As support bundles expand in scope within the control plane, consumers may need to select a version of bundle-cat compatible with a particular system release. A library crate would provide a straightforward way to pin that compatibility through a normal Rust dependency.

The existing command-line interface should remain available and retain its current behavior, while its parsing and filtering functionality moves behind a reusable public API. The library should also provide the ability to access bundle contents through a small source abstraction rather than depending directly on ZipArchive, enabling ZIP files, unpacked directories, and consumer-provided storage backends.

Requirements

• Add a bundle-cat-lib crate containing the reusable parsing, filtering, and data-model functionality.
• Retain bundle-cat as a thin CLI built on the library, preserving its existing arguments, behavior, and textual output.
• Provide documented, structured APIs so consumers do not need to parse CLI-formatted text.
• Expose reusable parsing primitives for stable support-bundle formats where appropriate.
• Support ZIP-backed bundles, unpacked directories, and consumer-provided storage implementations through a common source abstraction.
• Add tests demonstrating equivalent behavior across supported bundle sources.
• Preserve and extend existing tests to verify that the CLI continues to behave as before.