nibbler v0.1 reads the disk

Built the first working version of nibbler. The tool opens a WOZ 2.0 image, walks every track at the nibble level, identifies sector prologue sequences (standard and non-standard), reads sector data, verifies checksums, and produces a track-by-track report.

Ran it against the Apple Panic disk image. Output:

Track  0: 16 sectors, prologue D5 AA 96, all checksums valid
Track  1: 16 sectors, prologue D5 AA 96, all checksums valid
Track  2: 16 sectors, prologue D5 AA 96, all checksums valid
Track  3: 16 sectors, prologue D5 AA AD, all checksums valid
Track  4: 16 sectors, prologue D5 AA AD, all checksums valid
...
Track 34: 16 sectors, prologue D5 AA AD, all checksums valid

Tracks 3–34 all show the non-standard D5 AA AD prologue we found in January. Every checksum is valid. The disk is not damaged — the non-standard prologues are intentional, written deliberately to the protection tracks.

The tool also dumps the VTOC, lists file entries from the catalog, and can extract individual sectors to a file. It’s enough to be useful for anyone studying other Apple II protection schemes.

A few things nibbler can’t do yet: it doesn’t understand the XOR encoding on the HELLO program, and it doesn’t implement the custom RWTS to actually execute the protection. That’s documentation work, not tooling work — the articles cover the mechanism in full.

Will clean up the CLI and write proper help text before the Part 5 article publishes. Planning to release the source alongside the final article.