Merge PR #1223

# Conflicts:
#	crates/catalog/src/lock.rs
#	docs/parity-checklist.md

docs/arw6-compression.md

@@ -12,6 +12,7 @@ The codec is Sony's use of SMPTE RDD 34 (LLVC, Low Latency Video Codec). `crates
 
 - Raw SubIFD: Compression 32766, 14 bits per sample, BlackLevel 512 x4 (`0x7310`), WB `0x7313`, crop `0x74c7/0x74c8` (full frame: origin 12,8, size 9984x6656; APS-C: origin 16,10, size 6528x4352), CFA RGGB. The Sony tag-based white level (15360) is not read; the DNG `WhiteLevel` is (16383).
 - The single strip starts with a tile table: `u32` count, `u32` 0, then per tile a `u64` offset (relative to the strip) and `u32` x, y, width, height. Seen: full frame 4 tiles of 5008x3336 (HQ) or 5024 / 4992 wide (Compressed); APS-C (6592x4372) one tile. Bytes up to offset 512 follow the table (480 on APS-C, 408 on full frame; not interpreted, not needed).
+- Header mode (the import probe) reads the tile table and, per tile, the picture and group tables, the 13 stream header words, every stream's index table and the residual stream's first half — a few tens of kilobytes scattered through a 30-63 MB strip, which `lightcraft_raw::sparse::header_plan` keeps (the rest of the strip is skipped; the full-size JPEG the file also carries as a `JPEGInterchangeFormat` image is skipped too). The equivalence over `corpus/raw/**` is asserted by `crates/raw/tests/sparse_corpus.rs` and, without the corpus, `crates/raw/src/sparse.rs`'s synthetic single- and two-tile tests.
 - A tile is a sequence of 16-byte words. Word 0 is RDD 34 `Picture_info` (HS = tile width, VS = tile height / 2, BBD = 16, NC = 3, NW = 3, NP = `1000000000b`; other values are refused as unsupported). Word 1 holds five `u24` group byte-sums, word 2 is zero, words 3-7 describe the groups (a count byte, then `u24` stream sizes in words). Groups: g0 = LL3 (3 streams, one per component), g1 / g2 / g3 = level-3 / 2 / 1 bands (3 streams each), g4 = green residual (1 stream). Streams follow in that order from word 8.
 - A stream is a header word (a `u16` count of index words, a `u24` count of data words, then 11 bytes that are not interpreted), an index table and data, each padded to a word. The index has one entry per transform unit (TU): `A(16) X B(16) X`, where A and B are the byte lengths of the TU's two halves and X are quantiser-index (QI) nibbles (one for g0 and g4, three for g1-g3: HL, LH, HH). Halves per tile = ceil((VS - 2 - s) / 8) + 1 with s the first-half shift (below), TUs = ceil(halves / 2): 105 and 137 for the sample sizes. Halves are numbered n = 2 * TU + h; each is byte-aligned and consecutive halves are contiguous.
 - QI values seen, identical in Compressed and HQ files: level 1 component 0 (1,1,2), components 1-2 (2,2,3); level 2 (0,0,1); level 3 (0,0,0); LL3 0; residual 2. Compressed and HQ differ only in the coefficient data.