Acquisition Planning and Duplicate Prevention

[niklhut]

Release phase: after 1.0.

Deepen the "Acquisition Gap" pitch after basic wishlist states exist by helping users avoid duplicate purchases and make better buy/borrow decisions.

Scope

• Show duplicate warnings when adding by ISBN/manual entry/import/scanner.
• When a scanned or searched book already exists as owned or wishlisted, present a clear next action instead of failing silently.
• Add optional acquisition notes for wishlisted books:
  • Preferred format.
  • Source/store/library note.
  • Priority or someday/maybe status if useful.
• Add import behavior for wishlist/acquisition state once CSV supports states.
• Consider lightweight "already owned" checks from the scanner flow before adding another copy.

Acceptance

• Users get clear feedback when trying to add a book they already own or have wishlisted.
• Duplicate handling works across ISBN lookup, manual entry, scanner, and CSV import where applicable.
• Wishlist-to-owned conversion remains the preferred path when acquiring a wishlisted book.
• Tests cover duplicate detection and state-aware add flows.
• pnpm lint:fix, pnpm typecheck, and pnpm test:unit pass.

Notes

• This is post-1.0 unless duplicate purchasing becomes a major beta complaint.
• It depends on the Wishlist and Library States sprint; do not build this first.

[niklhut]

Planning context from the replacement wishlist/library-state work in #199, plus follow-ups #200 and #201:

• Duplicate prevention should build on the shared library_state model introduced in Wishlist and Library States #199, not introduce a parallel acquisition status model.
• If a book is already wishlisted and the user tries to add/acquire it as owned, the flow should surface that state and offer conversion/promotion to owned instead of failing or creating a duplicate active row.
• Future state-aware add flows should account for historical states from Previously Owned State and Saved Library State Filters #200, e.g. if a book is previously_owned, the user may need an "own again" path rather than a duplicate record.
• loaned out should remain a derived availability status from active loans, not a persisted library/acquisition state.
• Wishlist acquisition notes, preferred format, source/store/library notes, priority, and richer duplicate warnings belong here in Acquisition Planning and Duplicate Prevention #60 after the owned/wishlist foundation exists.
• For classification like fiction, art, psychology, etc., prefer first-class tag UX over separate category lists; see Make Tags First-Class Library Browsing Controls #201.