Raw-file consumers (punk-runtime 'platforms -remote'; third-party mirrors
using this layout) have no directory-listing capability - platforms.txt
lists the served platform folders, one canonical punkshell platform-dir
name per line ('#' comments/blanks ignored). Generated and kept current
by src/build_sha1sums.tcl (rewrite-on-change, matching the sha1sums
behaviour); os_list extended with openbsd/msys per the punkshell platform
canon, and the skip-message stale-variable reference fixed ($f ->
$dirtail). Documented in AGENTS.md Local Contracts.
Assisted-by: harness=claude; primary-model=claude-fable-5; api-location=anthropic.com
