feat: add safe Level.sav editing support

[bvoo]

Summary

Adds safe Palworld 1.0 Level.sav editing while preserving the existing GlobalPalStorage.sav workflow.

• Loads local player Palboxes, party/travel Pals, and working/base Pals from Level.sav with matching Players/*.sav context.
• Clones/imports Pals by updating the character map, target container slot, and guild handle together.
• Deletes Pals only when character, container, and guild references are structurally consistent.
• Fails closed for missing/stale player saves, full or malformed containers, player-shaped sources, duplicate IDs, and duplicate guild references.
• Caps compressed save input and decompressed GVAS output at 512 MiB for world and player saves.
• Writes through an exclusive same-directory temporary file, verifies the loaded target immediately before replacement, and installs with an atomic filesystem replace. A narrow race with an uncooperative external writer remains a documented platform limitation.

Save-integrity behavior

• Capacity is bounded by SlotNum, with unique in-range slot indexes.
• Batch imports preflight the entire operation and roll back if any insertion fails.
• Unknown and untouched save properties remain preserved.
• Existing backups remain part of the normal save flow.
• Serialization is verified by compressing, decompressing, byte-comparing, fully reparsing, and serializing the reparsed GVAS again before disk replacement.

Verification

• python -m unittest discover -v — 51 tests passed.
• python -m compileall -q PalEdit.py palworld_pal_edit palworld_save_tools tests — passed.
• git diff --check — passed.
• Source GUI startup smoke test — passed.
• Static added-line security scan — no secrets, shell execution, eval/exec, unsafe pickle, or SQL construction found.
• Public v1_relics/Level.sav fixture:
  • no-op output was byte-identical;
  • clone output reparsed with matching character/container/guild references;
  • deleting the clone restored the original raw GVAS bytes exactly.

Packaging note

The repository's pre-existing PyInstaller one-file build still does not bundle the native ooz module. Source execution and save verification work; this PR does not claim to fix that separate packaging issue.