feat: expand gen2D deck with deep technical slides and interactive elements

- Add 5 new slide pages: eino-deep-dive, ratelimit-overview, ratelimit-lua, async-deep-dive, harness
- Add 4 new drawio SVGs: pipeline-detail, ratelimit, async-task, harness
- Update all existing slides with v-clicks progressive reveal
- Add presenter notes and interactive prompts
- Expand slides.md to register all new pages (16 → 25+ slides)
- Fix text overflow by trimming content per Item block
- Add Eino Graph deep dive: WithGenLocalState, Pre/Post Handler, branch routing
- Add rate limiting section: algorithm comparison, Lua script, Gin middleware
- Add async task deep dive: TaskQueue FIFO, context progress injection
- Add consistency section: style/pipeline/data/deployment 4-layer guarantees

decks/gen2D/pages/ratelimit-lua.md

@@ -0,0 +1,60 @@
+# 令牌桶 — Redis Lua 脚本
+
+原子操作，单次 Redis 往返
+
+<div class="mt-2">
+
+```lua {1-2|4-8|10-14|all}
+local data = redis.call('HMGET', key, 'tokens', 'ts')
+local tokens = tonumber(data[1])
+local last_ts = tonumber(data[2])
+-- 首次访问，初始化满桶
+if tokens == nil then
+    tokens = burst
+    last_ts = now
+end
+-- 计算时间差，补充令牌
+local delta = now - last_ts
+if delta > 0 then
+    local refill = (delta * rate) / 1000
+    tokens = math.min(burst, tokens + refill)
+end
+```
+
+</div>
+
+<v-clicks>
+
+<Item title="为什么用 Lua 脚本？">
+整个令牌桶逻辑（读取 → 计算 → 扣减 → 写回）在 Redis 服务端原子执行，避免竞态条件。单次网络往返，性能最优。
+</Item>
+
+<Item title="关键逻辑">
+**初始化**：首次访问设满桶令牌。**补充**：按时间差 × 速率补充，上限为 burst。**扣减**：请求到达时 tokens - 1，不足则拒绝。
+</Item>
+
+</v-clicks>
+
+---
+
+# 限流中间件集成
+
+Gin 中间件 + 统一错误格式
+
+<Item title="中间件签名">
+`func RateLimit(limiter Limiter, keyFunc func(c *gin.Context) string) gin.HandlerFunc` — 可配置的 key 提取函数，支持按用户ID、IP、端点等维度限流。
+</Item>
+
+<Item title="注册方式">
+
+- **用户级**：auth 路由组，key = userID，保护个人配额
+- **全局级**：`/generate` 端点，key = endpoint，保护总容量
+
+</Item>
+
+<Item title="响应规范">
+
+- 通过：设置 `X-RateLimit-Remaining` 头
+- 拒绝：HTTP 429 + `Retry-After` 头 + 统一 JSON 错误体
+
+</Item>