Story 50: Unified Current Work Directory

- Move current/ to .story_kit/current/ (out of stories/)
- Type-aware routing for bugs, spikes, stories
- close_bug_to_archive() for bug lifecycle
- All path references updated across agents.rs, workflow.rs, mcp.rs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/http/mcp.rs

@@ -781,7 +781,7 @@ fn tool_get_story_todos(args: &Value, ctx: &AppContext) -> Result<String, String
         .ok_or("Missing required argument: story_id")?;
 
     let root = ctx.state.get_project_root()?;
-    let current_dir = root.join(".story_kit").join("stories").join("current");
+    let current_dir = root.join(".story_kit").join("current");
     let filepath = current_dir.join(format!("{story_id}.md"));
 
     if !filepath.exists() {
@@ -1401,7 +1401,7 @@ mod tests {
     #[test]
     fn tool_get_story_todos_returns_unchecked() {
         let tmp = tempfile::tempdir().unwrap();
-        let current_dir = tmp.path().join(".story_kit").join("stories").join("current");
+        let current_dir = tmp.path().join(".story_kit").join("current");
         fs::create_dir_all(&current_dir).unwrap();
         fs::write(
             current_dir.join("1_test.md"),