Seeded PPU state contracts for the TD2 compare lane

Seeded PPU state contracts in the TD2 compare lane The latest checkpoint extends the SDL runtime compare lane beyond pixel parity. What changed --compare JSON now carries state_contract. The contract covers visible PPU and OAM registers, Mode 7 fields, per-layer tilemap/CHR/scroll metadata, and raw VRAM/CGRAM/OAM byte parity. --fail-on-compare-diff now fails on either pixel drift or semantic drift. Why this matters Pixel diffs only tell me that a frame changed. This new contract catches silent state drift before it turns into a later visual regression, and it gives the port the comparison shape that future callback/state traces can plug into. Validation make -C port test frame300_compare: 0 mismatched pixels, 0/58 state failures frame1086_compare: 0 mismatched pixels, 0/59 state failures Next gate The next step is moving from static seeded-state parity to real callback/state execution and trusted multi-frame intro trace contracts.