Allow editing a Pal's XP value

[bvoo]

Summary

• adds an editable cumulative XP field below the Pal level
• shows current XP progress, XP remaining, and level/XP mismatches
• adds buttons for the current level's minimum XP, maximum XP, and deriving level from XP
• keeps XP in the save's signed IntProperty range and synchronizes XP when level changes

Motivation

PalEdit already updates XP automatically when changing a Pal's level, but it does not let users inspect or set the exact cumulative XP value. The progress tools make deliberate mismatches visible without blocking raw XP edits.

Changes

• add GetExp and SetExp to PalEntity
• route level-based XP updates through SetExp
• add an XP entry that commits on Enter or focus loss
• calculate cumulative progress and XP remaining for levels 1 through 80
• warn when XP falls outside the selected level's valid range
• add Level minimum, Level maximum, and Level from XP controls
• document cumulative XP editing and add regression tests

Test plan

• python -m unittest discover -v (7 tests)
• python -m compileall -q PalEdit.py palworld_pal_edit tests
• PyInstaller build completes
• source application starts successfully with python PalEdit.py
• independent staged-diff review passed with no security or logic findings

Notes for reviewers

The existing one-file PyInstaller output still cannot start without bundling the vendored ooz native module. The source application startup smoke test passes, and this PR does not change packaging.