Optimize `build_player_lookup` and `_lookup_pid` in strategy.py

[alhart2015]

Optimize build_player_lookup and _lookup_pid in strategy.py -- build_player_lookup uses iterrows() on ~5700 rows (~30-50ms per call, called ~12 times per pick). Replace with to_dict("index"). _lookup_pid does O(n) DataFrame scan per call -- build a name->pid dict once instead. Several strategies already build player_lookup but don't pass it through to _lookup_pid.

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Migrated from TODO.md (section: postseason) on 2026-07-09. TODO.md is being retired in favor of GitHub Issues.