Tolerate retired settings fields, document iCloud venv hazard

_deserialize crashed on any saved league carrying a field ModelWeights/
Scoring/LeagueSettings no longer defines (found live: several leagues had
a stale td_luck weight) -- now drops unknown keys instead of raising, so
schema changes don't brick existing leagues.

Also identified the root cause of the "hidden .pth" import failure:
Desktop/Documents iCloud sync tags the editable install's .pth file
hidden and keeps re-hiding it. Documented that in troubleshooting.md and
pointed claude_desktop_config.json + README at a non-synced venv location.