spec: delta wire form is grouped; status cadence has out-of-cadence reports

docs/superpowers/specs/2026-10-30-vt1200-video-streaming-design.md

@@ -182,9 +182,10 @@ frame start, so a frame never straddles the ring wrap and slot ownership is expl
 * **Dictionary**: 256 × 32×32 1-bpp (128 B each = 32 KB), built offline by k-means
   over the video's tiles, uploaded in chunks, held in the startup allocation.
 * **Frame**: header + 1,280 index bytes (40×32 grid, row major). `kind = TILES_FULL`.
-* **Delta**: `kind = TILES_DELTA` + a changed-tile list: `count u16`, then
-  `count` × (`pos u16`, `index u8`) little-endian, where `pos` is the row-major
-  tile position and `index` its new dictionary entry. Deltas are the normal case.
+* **Delta**: `kind = TILES_DELTA` + a changed-tile list in three blocks, little-endian:
+  `count u16`, then `count` × `pos u16`, then `count` × `index u8`; `pos` is the row-major
+  tile position and `index` its new dictionary entry. Grouped rather than interleaved, so the
+  decoder validates all positions before it paints anything. Deltas are the normal case.
 * Decoder: one cached loop; `PIXBLT B,XY` from `dict + index*128`, `DYDX=(32,32)`,
   `SPTCH=32` (a 32-px row is **two** words), destination XY `(ty*32, tx*32)`.
 * **Repair**: a `TILES_FULL` keyframe every 2 s (and on the host's first frame), so
@@ -192,8 +193,11 @@ frame start, so a frame never straddles the ring wrap and slot ownership is expl
 
 ### 8.4 Host ↔ terminal back-channel
 
-The payload already has TX. It sends a small status frame every 64 frames:
-frames received, `crc` failures, drops, `CSR0` error bits, and the worst decode time.
+The payload already has TX. It sends a small 16-byte status body every 64 frames — frames
+received, `crc` failures, drops, `CSR0` error bits, heap free, a `dict_state` byte, and the worst
+decode time in REFCNT ticks (the TMS34010 refresh counter, not µs) — plus an out-of-cadence report
+after the first accepted frame and after any refused dictionary chunk, so a failed upload is
+diagnosable instead of looking like a payload that never started.
 The host uses it to pace the stream and to force a keyframe when drops are seen.
 **Call:** status every 64 frames (~2 s at 30 fps); no per-frame ack.