+ add R/W Apple II Binary II archives - #124

What changed

Adds Apple II Binary II / BLU (.bny / .bqy) as a first-class archive format.

• version-1 128-byte record headers (0A 47 4C, secondary 02 marker)
• ProDOS-style partial path handling with deterministic normalization
• explicit directory records before descendants
• stored member creation
• Squeeze member creation via the existing managed FileFormat.Squeeze building block
• auto mode chooses Squeeze only when the 128-byte-rounded stored extent is smaller
• historical BLU .QQ Squeeze fallback when the compressed data flag is absent
• encrypted and undefined sparse records are listed but extraction refuses rather than guessing
• phantom records participate in physical layout/countdown but are not exposed as ordinary files

Genuine R/W

CanModify is intentional. Binary II members are independently framed as 128-byte header + payload rounded to 128 bytes, so modification does not require extract/re-create:

• add appends new physical records and repairs files-to-follow countdown bytes
• replace rewrites the target record and shifts only the following tail when its rounded extent changes
• remove shifts only the following tail left and truncates
• directory removal also removes descendants
• untouched stored/compressed member payloads are never decoded or re-encoded

The reader treats files-to-follow as metadata rather than the only parse delimiter so stale counters can be repaired safely during direct mutation.

Layout / cleanup

Implements IArchiveLayoutMap for per-record headers, payloads, and 128-byte padding. Defragmentation zeros member padding and trims trailing transport garbage without rewriting payloads.

Tests

Coverage includes stored and Squeeze round trips, BLU .QQ compatibility, directory synthesis, direct add/replace/remove, countdown repair, auto compression, ProDOS path normalization, encryption rejection, and trailing-padding cleanup.

Format layout and historical behavior were cross-checked against Apple II File Type Note $e0/8000 as documented by CiderPress II; Squeeze uses the repository's existing managed implementation.