DKR-R 1.0.5 Beta 15 - Playtest 15 Fix 1

HISTORICAL BUILD RECORD
The original findings and limits below belong to the named earlier build.
For current instructions, use docs/README.md and CHANGELOG.md in the
source repository. These old results do not qualify later packages.


Track Select and failed-session retry correction

- A pending stock track preview is an explicit restoration of retail assets,
  represented by an empty mod identity. Its rollback checkpoint now restores
  that request only for retail level IDs 0-64, instead of rejecting it as an
  unadmitted custom course. Custom IDs/carriers remain strictly catalog-bound.
- Fresh host/join connections clear a previous failed match's launch roster,
  retired experimental generations, native receive queue and pending save
  completions. Same-lobby retirement and conflicting-start checks stay intact.
- Predictive menu animation, rollback performance improvements, image quality,
  legacy backend protocols, installed mods and separate offline saves are kept.

All racers should update to this corrected build before testing together.
Verification is headless; real-device and Internet gameplay remain playtests.
This correction is not a claim that every online edge case is now bug-free.
