Remove self link in RWP packages

[mickael-menu]

A manifest.json embedded in an RWP package may contain a self link (e.g., if it is packaged from a streamed manifest). This conflicts with the resolution of local relative HREFs, so this PR removes the self link.

• Fixes [Bug] Not playing audio for the .audiobook format #626

[Copilot]

Pull Request Overview

This PR ensures that any self link embedded in a streamed manifest is removed before building the Publication, preventing conflicts with local relative HREF resolution.

• Introduce a mutable copy of manifest in the mapping closure
• Filter out any links whose relation contains .self
• Proceed with building the Publication using the updated manifest

Comments suppressed due to low confidence (1)

Sources/Streamer/Parser/Readium/ReadiumWebPubParser.swift:109

• No tests cover the removal of .self links from the manifest. Adding a unit test for this filtering behavior would help prevent regressions.

                manifest.links = manifest.links.filter { !$0.rels.contains(.self) }