feat: rename bugfix-ship/requirement-flow to short-ship/long-ship with shared ship records

short-ship and long-ship share one ship-id record under .pouch/ship/<id>/.
specifier writes PRDs into spec/; delivery-loop appends evidence pointers.
Old names stay as deprecation stubs so existing installs keep working.

skills/builder/references/obtain.md

@@ -5,7 +5,7 @@ docker / deb / android / ios / copy 仍是轨道；`BUILD_VENUE` 只说明构建
 
 ## 谁来调用
 
-- `bugfix-ship` 和 ACK 走到 delivery-loop 的 `artifact_built` 时。
+- `short-ship` / `long-ship` 和 ACK 走到 delivery-loop 的 `artifact_built` 时。
 - 用户说「看构建」「监听 CI」「拿到镜像」时。
 - `make -f makefile.builder obtain` 或 `push-docker`（`BUILD_VENUE=ci`）。