Port from earendil-works/pi#8337 (UTF-8 BOM normalization in text inputs):
sibling sites the merged #81967 BOM sweep missed. json.loads hard-fails on
a leading U+FEFF and every one of these loaders swallows the exception and
silently falls back to defaults — a user who edited mem0.json, honcho.json,
hindsight/config.json, or supermemory.json in Notepad lost their whole
config with no error, and Qwen CLI OAuth creds saved with a BOM raised
qwen_auth_read_failed.
- plugins/memory/{honcho,mem0,hindsight,supermemory}: 13 read sites -> utf-8-sig
- hermes_cli/auth.py: _read_qwen_cli_tokens -> utf-8-sig
- tests: BOM regression tests per loader (sabotage-proven) + plain-UTF-8 guard
