CI / build + unit + e2e (pull_request) Successful in 2m33s
Adds the sea ability: a fixed set of 12 named sea zones with sole-control semantics, contest-by-higher-military, and a deterministic per-turn +1 military/+1 economy bonus for each claimed zone. Durable (owns GameState.seaZones), additive migration, stub-inert (e2e unaffected). Fixes #65 Design note: Gitea #65 sketched a free-form 'naval' layer; the implemented approved design is this richer 'sea' layer with a fixed zone set.