Fix observation pipeline contract (resolution, layout, normalization)

[thopkins32]

• Forge captures full window size via glReadPixels; Python parse_observation expects ConnectionConfig.frame_height * frame_width * 3. Mismatch causes failures or wrong reshapes unless the window is fixed to match config.
• engine.run builds tensors from HWC numpy without a documented permute to NCHW; vision tests use (B, 3, H, W) -- document and enforce one convention end-to-end.
• Optionally scale inputs to [0, 1] or documented stats for stable training.
• Acceptance: single doc + test or script that connects (or mocks) mod and asserts parsed frame shape matches engine.image_size and model input layout.