* fix(#1993): milestone --ws requirements archive header points at workstream path
The requirements archive header hardcoded the root .planning/REQUIREMENTS.md
path, so a workstream (--ws) archive pointed readers at the wrong file even
though #1917 fixed the archive LOCATIONS to land inside the workstream.
Derive the display path from the same workstream-aware reqPath the writer
already uses (path.relative(cwd, reqPath)). Root behavior is byte-identical
('.planning/REQUIREMENTS.md'); the --ws case now correctly reads
'.planning/workstreams/<ws>/REQUIREMENTS.md'.
- src/milestone.cts: reqDisplay interpolation in the archive header.
- tests/milestone.test.cjs: #1993 regression in the #1911 --ws block — header
references the workstream path, not the root literal.
Closes#1993
* docs(#1993): backfill changeset pr 2015
* fix(#1993): use posix separators in archive header (Windows CI) + CRLF-safe test split
- src/milestone.cts: normalize path.relative output to POSIX separators so
the workstream archive header renders forward slashes on Windows too
(path.relative yields backslashes there; the original literal was posix).
- tests/milestone.test.cjs: .split(/\r?\n/) for the CRLF-fragile lint rule.
