tests/read_only.rs: with every file and folder of the books read-only on
disk, the viewer loads, follows live, and renders every page (receipts
included), and every file keeps its bytes, size, and mtime; on writable
books nothing appears beside the database either.
Found: with no writer running, the snapshot's read-only open of the WAL
database had to create -wal/-shm (a write into the books) and failed on
read-only books, showing a false "database unreadable". With no -wal
file no writer has it open, so check_disk now reads it immutable.
just mutants-gui sweeps only what the viewer must get right: the view
model's numbers (books.rs) and their formatting (fmt.rs); 179 mutants.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX
