fix(workflow): sendNotification skip-on-empty-toUserId + error precision + doc unification

- toUserId 解析为空时静默跳过 (succeeded, sentCount=0, skipped:true) 而非 failed
  → 支持'仅有重复订单时才通知'的条件通知编排
- 必填校验只列出实际缺失字段 (message)，不再误报已解析的字段
- 文档统一变量格式: {{nodeId.path}} 为主，{{index.path}} 兼容
- spec 6/6，线上实测: 空收件人 skip + 非空正常发送均验证

.agents/skills/inkreach-teable/SKILL.md

@@ -132,7 +132,7 @@ These differ from official teable and from the (stale) `docs/automation/triggers
 2. **Read [trigger-types.md](api-reference/trigger-types.md) before configuring a trigger** — contains exact config keys per trigger; guessing leads to silent misfires.
 3. **Build the full chain then activate** — `workflow create` → `trigger set` → `action add` → `activate`. Editing nodes after activation requires re-`activate` to snapshot.
 4. **For `buttonClick`, ensure the field is a Button field bound to this workflow** — create via `field create --type button` with `options.workflow.id` (the `workflow` value is an **object** `{id, name?}`, NOT a bare `workflowId` string — matching the DB shape), or the field won't render/click. Note: field `options` captures a stale `isActive` snapshot at creation; the API validates the DB `isActive` at click time instead, so a deactivated workflow returns 400.
-5. **Read [action-types.md](api-reference/action-types.md) before writing scripts** — covers sandbox globals, variable references `{{nodeIndex.path}}`, and the `_accessToken`/`_apiBaseUrl` back-channel.
+5. **Read [action-types.md](api-reference/action-types.md) before writing scripts** — covers sandbox globals, variable references `{{nodeId.path}}`, and the `_accessToken`/`_apiBaseUrl` back-channel.
 
 ## 5. Common Errors & Recovery