Add replay system with scrub support and reusable render path

[eshaffer321]

Summary

Add a replay system that can load a recorded game log, play it back through the existing UI, and support scrubbing/jumping to any point in the game timeline.

Problem Statement

We need a way to review completed games without live user input driving the game. The current client/server architecture is close to replay-ready, but input handling and replay control need explicit support.

Current Behavior

• Game state is produced by the in-memory server and pushed to the client.
• UI renders from ClientGameState via context and Pixi/React components.
• User interactions (hex clicks, card clicks, etc.) dispatch actions directly through sendAction.
• No persisted replay log format exists today.

Expected Behavior

• A completed game can be exported/imported as a replay log.
• Replay mode can play/pause, step, and scrub to any timeline position.
• Existing board/hand rendering path is reused (state-driven rendering remains the source of truth).
• Input/gameplay actions are disabled while replay mode is active.

Investigation Findings

• Rendering is already largely state-driven and reusable for historical snapshots.
• Primary coupling is interaction binding in render-time overlay handlers and turn-gated input hooks.
• Engine/server are deterministic with seeded RNG, making action-sequence replay feasible.
• Server currently returns events + resulting state per action; this is a strong base for logging.

Proposed Technical Approach

1. Add replay log schema in shared types (versioned): metadata + initial seed + ordered actions.
2. Add optional periodic checkpoints (serialized state every N actions) to speed seek/scrub.
3. Add replay logger around server action handling.
4. Build replay controller/provider in client:
   • manages timeline index, play/pause, speed, seek/step
   • exposes effective state (live vs replay) to existing UI
5. Gate/disable gameplay dispatch and interactive handlers while in replay mode.
6. Add replay controls UI (timeline slider + step buttons + play/pause).

Affected Files

• packages/client/src/context/GameProvider.tsx
• packages/client/src/components/GameBoard/pixi/rendering/overlays.ts
• packages/client/src/components/GameBoard/hooks/useHexInteraction.ts
• packages/client/src/components/Hand/PlayerHand.tsx
• packages/client/src/components/GameBoard/hooks/useGameBoardRenderer.ts
• packages/server/src/GameServer.ts
• packages/shared/src/connection.ts
• packages/core/src/utils/rng.ts

Acceptance Criteria

• Define and document a versioned replay log schema in shared types.
• Record replay logs from completed games (initial seed + action sequence).
• Implement replay mode that drives UI from replay timeline state.
• Add controls for play/pause, step forward/back, and timeline scrub.
• Disable live input dispatch while replay mode is active.
• Reuse existing render pipeline for replayed states (no duplicate renderer).
• Implement seek performance strategy (checkpointing or equivalent) for long games.
• Add tests for deterministic reconstruction and seek correctness.

Rough Effort Estimate

• MVP (load log + play/pause + step + basic scrub): ~1-2 weeks
• Production-ready (fast seek, polish, import/export UX, test coverage): ~3-5 weeks total