`graphify prs` reads gh, git, and claude output via subprocess.run(text=True)
with no explicit encoding=, so on Windows stdout is decoded with the cp1252
locale codec. gh emits UTF-8 JSON whose PR titles and logins routinely carry
non-Latin1 bytes (emoji, or the Persian title in PR #1281), and cp1252 has no
mapping for bytes such as 0x81. The capture reader thread raises
UnicodeDecodeError, subprocess.run then returns stdout=None, and the caller dies
one line later on json.loads(None) (TypeError) or None.splitlines()
(AttributeError). Neither is caught by _gh's except clause, so the whole `prs`
command aborts, with a spurious reader-thread traceback on stderr, against any
repo that has non-ASCII PR metadata.
Pass encoding="utf-8", errors="replace" to all five subprocess reads in prs.py
so decoding matches Linux and macOS. This is the decode-side sibling of #1505,
which applied the same change to the llm.py claude-cli subprocess. CI runs Linux
only (a UTF-8 locale), so this path is never exercised there.
Reproduced on Windows 11 / CPython 3.13 with a cp1252 locale:
prs._gh("pr", "view", "1281", ...) crashed with TypeError before and returns the
decoded title after. The added regression tests assert encoding="utf-8" on each
call, mirroring tests/test_charmap_encoding.py, and are red without the fix.
