* feat(artifacts): add U-Boot legacy uImage reader (part of #7129)
Recognize legacy uImages by their 0x27051956 magic and inventory them as containers: 64-byte header facts (arch/os/type/compression raw and named, load/entry addresses, name, timestamp) with header and data CRC32 verified, stored payload extractable as payload.bin, and multi-file images split from the stored size table into image-<n>.bin. Compressed payloads stay as stored; nothing is executed or decompressed. Wires the format through classification, the artifact reader dispatch, extraction, and the evidence/snapshot format vocabularies. Related to #7129 (uImage part only); HEX/SREC and FIT are out of scope.
* fix(uimage): preserve aligned component ranges and exact header facts
* fix(uimage): retain buffered members through consumption and cancellation
* fix(uimage): preserve active read and validation failure precedence
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Co-authored-by: gensokyo-dev <[email protected]>
