Add modules/client_server_authority.md: default server truth for
persistence/economy/combat; intents vs state table; E1.M1–E1.M4 and
E5.M1 ownership; economy/quest/zone/PvP blanket; deferred tick rate
and lag comp.
Link from contracts.md, register, decomposition README, tech_stack;
one-line Authority pointers in E1_M1, E1_M2, E5_M1. Fix contracts.md
baseline link formatting.
Made-with: Cursor