rusty_h264-encoder-v0.17.0

Fixed

• the profile census compiles again, and the decoder builds no_std (#20)

Other

• make main green — fix the root cause behind each failing gate
• narrow the motion grids to (i16,i16) - 2.90 GB of pool clear removed
• four more, from the encoder and the PPS-gated grids
• narrow the reference-index grids i32 -> i8 (-103 MB of memset)
• overflow-checks cost 22.5% of decode — moved to release-checked
• audit pass 2 — 6% to 89% of in-scope gates, every unit >=85%
• close H-03/04/05/07/13/14/15/16/31/39 + threat model
• use-protection-please first pass — 41 gates x 8 units, depth=deep