Build authoritative Realm Chat V1

[ael-dev3]

Summary

Builds a modern, persistent Realm Chat V1 as a review-only implementation stacked on #178.

The design follows current game-chat patterns—compact gameplay-first UI, unread state, local mute, message-level reporting, and bounded history—while making SpacetimeDB the sole authority for sender identity, timestamps, global ordering, rate limits, idempotency, moderation state, and preserved report context.

What changed

• adds seven additive protocol-V15 tables with public/private separation
• adds caller-bound send, history, report, and admin moderation operations
• enforces exact rolling rate limits, duplicate throttling, bounded Unicode/byte/line policy, and replay-safe send receipts
• maintains a 128-message public live projection backed by a private authoritative archive
• preserves original message evidence for moderators while public tombstones remove body content
• adds a responsive desktop/compact Realm Chat dock with unread handling, load-older pagination, sender cards, locate, local mute, copy, report disclosure, keyboard/focus handling, and Mini App Back integration
• keeps chat out of the 10,000-cell world snapshot through its own small subscription
• updates generated/player bindings without exposing private chat tables
• adds the frozen V15 migration fixture and real disposable upgrade/rollback proof
• documents the architecture, abuse model, threat model, operational flow, research, and non-goals

Safety and rollout

This PR does not activate or deploy chat.

• client entry gate remains false
• server activation compile gate remains false
• production module publication now fails closed while Realm Chat V1 is review-only
• no production SpacetimeDB or website state was changed
• retention/deletion, appeals, moderator staffing/escalation, jurisdiction/age/privacy review, and final launch approval remain explicit blockers

Verification

• 2,989 application tests passed across 272 files
• 331 SpacetimeDB authority/migration tests passed
• protocol-V15 disposable migration proof passed on SpacetimeDB 2.6.1, including populated chat tables, prior-row preservation, rollback refusal, and post-upgrade worker/gameplay exercise
• generated binding verifier passed
• production build and asset/Farcaster/exclusion checks passed
• TypeScript checks passed for client and module
• committed-HEAD license/cutover guard passed
• SpacetimeDB production dependencies report no known vulnerabilities
• diff whitespace and secret-pattern scans passed

Stack

• Base: agent/realm-chat-legal-contract
• Legal/review contract: Draft Realm Chat legal and conduct contract #178
• This PR: implementation and assurance only