plan: align the remaining CRC text with R14 (header-only)

docs/superpowers/plans/2026-10-30-vt1200-stream-transport-and-row-strips.md

@@ -84,7 +84,7 @@ Expected: FAIL — `ModuleNotFoundError: harness.udpstream.frame`
 
 - [ ] **Step 3: Implement `frame.py`**
 
-Layout (little-endian): `'V','S'`, version `0x01`, `kind`, `frame_no` u16, `payload_len` u16, `rows` u8, `stretch` u8, 2 reserved, `crc16` u16 over header bytes 0..11 plus the payload. CRC is CCITT-FALSE: poly `0x1021`, init `0xFFFF`, no reflection.
+Layout (little-endian): `'V','S'`, version `0x01`, `kind`, `frame_no` u16, `payload_len` u16, `rows` u8, `stretch` u8, 2 reserved, `crc16` u16 over the 12 header bytes only (R14). CRC is CCITT-FALSE: poly `0x1021`, init `0xFFFF`, no reflection.
 
 - [ ] **Step 4: Run test to verify it passes**
 
@@ -149,7 +149,8 @@ Expected: FAIL — no module `vidsrc`
 
 - [ ] **Step 3: Implement `Rows.pack_row` and `StripSource`**
 
-`pack_row` sets bit `i` of the byte stream for pixel `i` (MSB first within each byte). `StripSource.encode` prepends `pack_header(KIND_STRIP, frame_no, len(rows), rows, stretch, payload=rows)` — **the payload must be passed so the CRC covers it**, or the terminal rejects every frame — and chunks the result at 1450 bytes.
+`pack_row` sets bit `i` of the byte stream for pixel `i` (MSB first within each byte). `StripSource.encode` prepends `pack_header(KIND_STRIP, frame_no, len(rows), rows, stretch, payload=rows)` (the payload is
+advisory under R14 — the CRC covers the header only) and chunks the result at 1450 bytes.
 
 - [ ] **Step 4: Run test to verify it passes**
 
@@ -237,9 +238,10 @@ into a slot and asserts the payload's counters. The real DMA path is proven in T
 
 `tests/test_frame_parse.c`: build a 16-byte header + payload with the same layout `frame.py`
 writes (magic 'V','S', version 1, kind 1, frame_no, payload_len, rows, stretch, CRC16 at offset
-12 over bytes 0..11 + payload). Assert `fp_parse` accepts it; flip one payload byte and assert it
-is rejected; truncate it below `16 + payload_len` and assert rejection; corrupt the magic and the
-version and assert rejection.
+12 over the 12 header bytes). Assert `fp_parse` accepts it; flip one payload byte and assert it is
+**still accepted** (the body is protected by the Ethernet FCS, R14); truncate it below
+`16 + payload_len` and assert rejection; corrupt the magic, version and a header byte and assert
+rejection.
 
 - [ ] **Step 2: Run it to verify it fails**
 
@@ -250,7 +252,7 @@ Expected: link error, `fp_parse` undefined.
 
 K&R-compatible C89 that also compiles with the 1987 compiler: no `//`, no declarations after
 statements, CRC16 CCITT-FALSE as in `frame.py`. `fp_parse` checks length first, then magic and
-version, then CRC over `buf[0..11] + payload`.
+version, then CRC over the 12 header bytes only (R14).
 
 - [ ] **Step 4: Run the host test to verify it passes**