story-kit: create 151_story_split_archived_into_done_and_archived_with_time_based_promotion

.story_kit/work/1_upcoming/151_story_split_archived_into_done_and_archived_with_time_based_promotion.md

@@ -6,11 +6,31 @@ name: "Split archived into done and archived with time-based promotion"
 
 ## User Story
 
-As a ..., I want ..., so that ...
+As a developer watching work flow through the pipeline in my IDE, I want recently completed items separated from old ones, so that the folder view stays useful without being cluttered by dozens of ancient stories.
+
+## Description
+
+The `5_archived` folder has grown huge and clutters the IDE sidebar. Split it into two stages:
+
+- `5_done`: recently completed work — visible in IDE, useful for watching flow
+- `6_archived`: old work moved here automatically after 4 hours
+
+The watcher should periodically check `5_done/` and move items older than 4 hours (based on file mtime) to `6_archived/`.
+
+### Key Files
+- `server/src/io/watcher.rs`: filesystem watcher — add periodic sweep of `5_done/`
+- `server/src/agents.rs`: `move_story_to_archived` → rename to `move_story_to_done`, target `5_done/`
+- All MCP tools and pipeline logic that reference `5_archived` need updating to use `5_done`
+- Frontend pipeline display if it shows archived/done items
 
 ## Acceptance Criteria
 
-- [ ] TODO
+- [ ] `5_archived/` is renamed to `6_archived/`
+- [ ] New `5_done/` directory is created and used as the immediate completion target
+- [ ] Mergemaster, accept_story, and all pipeline functions move completed work to `5_done/` (not directly to archived)
+- [ ] Watcher periodically sweeps `5_done/` and moves items older than 4 hours to `6_archived/`
+- [ ] Existing items in old `5_archived/` are migrated to `6_archived/`
+- [ ] Frontend pipeline display updated if applicable
 
 ## Out of Scope