docs(plan): code-grounded parallel dev-task breakdown (subagent→codex loop, 8.3/8.0/8.0)

Decomposes the demo-previewed roadmap into collision-free lanes by file domain
so the team can develop in parallel. 4 rounds of subagent-edit → codex-review
(需大改 → 需小改 → 可收敛):

- 7 lanes by file domain (P Platform/Deploy · A GameEngine · B Arena contracts ·
  C PredictionMarket · D MCP/keeper/infra · E wallet/write client · F read/visual);
  disjoint-file-domain table — every contested file (chain.ts→D, useArenaEngine.ts→F,
  app/me shell→E + ledger components→F, app/arena/market→E) has exactly one owner
- new Lane P (Router slot / Deploy+Upgrade scripts / operator authorization / address+ABI sync)
- Auth/Delegation decision gate: AgentRegistry operator is GLOBAL + onlyOwner — there is
  NO per-agent delegation, so "owner→operator 委托开关 (可收回)" needs either a global
  operator + off-chain toggle (default) or a new per-agent delegation task (A3)
- gates + critical path corrected; make-the-demo-real mapping flags contract prerequisites
  (ability viz needs trace instrumentation B2; provenance needs Card metadata B3)
- fixed stale facts vs current code (demo 2604 lines, existing Arena keeper, frontend
  reads ledgers via direct RPC not MCP, chain.ts event ABI drift, existing listing tools)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: keanji-x