Sets up ESLint 10 flat config with @typescript-eslint/no-floating-promises (error) and no-console (warn, allow warn/error). Fixes all floating promise errors in server routes, orchestrator reader cleanup, and frontend composables with void operator. Game engine files get warning-level for intentional fire-and-forget async. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>