fix: reset big fish initial creation progress

docs/technical/PUZZLE_BIG_FISH_INITIAL_CREATION_PROGRESS_ZERO_FIX_2026-04-26.md

@@ -26,3 +26,7 @@
 2. 新建拼图创作工作区后，顶部创作进度显示 `0%`。
 3. 发送第一条用户消息后，进度按模型回包或后续操作正常推进。
 4. 生成草稿、生成资产、发布等后续阶段的进度值不受本次调整影响。
+
+## 2026-04-27 复核记录
+
+大鱼吃小鱼创建链路曾回退为 `progress_percent = 20`。本次重新将 `create_big_fish_session_tx` 的初始进度锁定为 `0`，并用 `INITIAL_BIG_FISH_CREATION_PROGRESS_PERCENT` 常量表达该约束，避免欢迎语或初始锚点占位再次被误计为创作进度。

server-rs/crates/spacetime-module/src/big_fish/session.rs

@@ -1,6 +1,8 @@
 use crate::big_fish::tables::{big_fish_agent_message, big_fish_creation_session};
 use crate::*;
 
+const INITIAL_BIG_FISH_CREATION_PROGRESS_PERCENT: u32 = 0;
+
 #[spacetimedb::procedure]
 pub fn create_big_fish_session(
     ctx: &mut ProcedureContext,
@@ -182,7 +184,8 @@ pub(crate) fn create_big_fish_session_tx(
             owner_user_id: input.owner_user_id.clone(),
             seed_text: input.seed_text.trim().to_string(),
             current_turn: 0,
-            progress_percent: 20,
+            // 中文注释：欢迎语和初始锚点只建立工作台上下文，不能提前抬高创作进度。
+            progress_percent: INITIAL_BIG_FISH_CREATION_PROGRESS_PERCENT,
             stage: BigFishCreationStage::CollectingAnchors,
             anchor_pack_json: serialize_anchor_pack(&anchor_pack)
                 .map_err(|error| error.to_string())?,
@@ -707,6 +710,11 @@ mod tests {
         }
     }
 
+    #[test]
+    fn initial_big_fish_creation_progress_starts_from_zero() {
+        assert_eq!(INITIAL_BIG_FISH_CREATION_PROGRESS_PERCENT, 0);
+    }
+
     #[test]
     fn big_fish_direct_work_content_ignores_empty_created_session() {
         let empty_session =