utf-8-sig exists to tolerate BOMs that Windows tooling adds to files
users edit. /proc and /sys files are generated by the Linux kernel, never
BOM'd and absent on Windows, so -sig there only muddies the read/write
policy. Switch every literal /proc/ and /sys/ read to utf-8 and teach
the footgun read rule that string literals starting with /proc/ or
/sys/ are exempt (user-edited files keep utf-8-sig).
Read text files with the encoding utf-8-sig so a BOM at the start of a
file does not cause a Unicode decode error (Windows editors add BOMs).
Reconstructed from ethie/pm commits 48a32b135b + 013219e814 onto the
current upstream/main base: only the utf-8 -> utf-8-sig transforms were
carried (370 exact line pairs across 205 files); pm-rename hunks that
rode in the original commit were left to the pm-store commit, and
utf8sig hunks entangled with content changes ride their owning commit.
Rebuilt on ethie/pm-clean off ac6c8028e0 (upstream/main).
