Unity foundation and content integration harness

[YIFNEN]

Summary

• stop tracking the generated Windows build while keeping the local ignored build intact
• move legacy scripts into the maintained Unity workspace without changing their .meta GUIDs
• add project AGENTS contracts, four Home Protector skills, the canonical asset manifest, repository hygiene CI, and concise Unity/Git launchers

Current asset baseline

• 103 sheet candidates
• 101 included sheets plus 22 canonical single sprites
• Player Walk B05/B06 excluded as historical
• Bear B20 and BearHeavy B31 retained as distinct roles

Validation

• PASS asset-manifest sheets=101/103 singles=22 total=123
• PASS unity-repo-hygiene files=2521 assets=2465 manifest=125
• all four repo-local skills pass the official skill validator and pressure tests
• Unity EditMode is currently BLOCKED before tests because the local Unity entitlement expired

Pending before ready for review

• activate a Unity Personal license in Hub
• obtain the GameSession RED test result, implement the runtime transition fix, and run Unity validation
• checkpoint the existing isometric scene, prefabs, and pending Monkey/CoolDryer content without losing references