Piece registrations were centralized but creation, reference bookkeeping and
cleanup still lived in the library. Move creation/model reuse, normalization,
metadata renaming, reference operations, temporary cleanup, project transfer and
ordered identity teardown into the manager. Keep registration/deletion helpers
private and remove the temporary local-registry enumeration APIs.
The library remains the acquisition facade and coordinates source resolution,
loading, invalidation and cancellation after unlocking. Handles still bind to
the library. Clear sparse errors from lcPieceData::Unload before resource teardown
so manager deletion does not require a library pointer or callback. Sparse error
storage and the existing synchronization remain library-side.
Use one project-aware manager lookup, passing nullptr for shared-only searches.
Remove the maximum-size name reservation so short names can use inline storage.
Replace remaining bounded C-string copy/terminator pairs with lcstrcpy and record
the helper convention in common/AGENTS.md. Update the asset lifetime documentation.
Validation: macOS Qt 6.10 Debug build, whitespace checks and 40 offscreen lifecycle
checks, including already-zero release, last-owner cancellation, model reuse,
project detach/transfer cleanup, sparse errors, archive/directory caches and forced
nested external-project teardown. Successful GPU rendering is not covered by the
offscreen checks.