feat(core): add Wandering Inn parser

[audemed44]

Summary

• port the Wandering Inn parser behavior from WebToEpub into epubForge core
• add a dedicated WanderingInnParser for wanderinginn.com
• wire parser registration so https://wanderinginn.com/table-of-contents/ is auto-detected
• preserve Wandering Inn-specific content handling (#reader-content, title filtering for "loading...", mrsha italics, iBooks dark-theme color class)

Validation

• npm run typecheck
• live preview check for https://wanderinginn.com/table-of-contents/ returns parser wanderinginn and 808 chapters