Add render_dx10.cpp (selectable as `dx10`): composes the animated pattern
(background + moving bar + top-left frame-counter block) on the CPU each frame
and CopyResource's it into a real D3D10 DXGI swap-chain back buffer (DX10 has no
rect-clear; no shaders). Smoke-verified: `coop_mock_game dx10 2` presents frames
and exits cleanly. The frame-accurate decode-through-the-hook assertion lands
with the DX10 capture commit next.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
