CLAUDE: rung C2 - prepare upload groups nullable (configuration registers)

Design 3-A4i rung C2: tp_proc_exec_pose_lma_prepare_resident treats its
uploads as three nullable groups - NULL = keep the resident copy, guarded by
pose_prep_ready bits: reference camera block + centers (per-SEQUENCE), scene
camera block (per-SCENE). Per-cycle payload shrinks to pose_vectors + 6
policy floats + the 8-float result D2H. Tile-capacity regrows clear the
centers ready bit (both entry points). Camera meta now uploads per half.
Gates: full suite PASS (direct step+prepare bit-exact, NVRTC x3, pose_corr
@tol 0, sanitizer 0 errors).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>