rename .story_kit directory to .storkit and update all references

Renames the config directory and updates 514 references across 42 Rust
source files, plus CLAUDE.md, .gitignore, Makefile, script/release,
and .mcp.json files. All 1205 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/http/mcp/merge_tools.rs

@@ -138,7 +138,7 @@ pub(super) fn tool_report_merge_failure(args: &Value, ctx: &AppContext) -> Resul
     // survives server restarts and is visible in the web UI.
     if let Ok(project_root) = ctx.state.get_project_root() {
         let story_file = project_root
-            .join(".story_kit")
+            .join(".storkit")
             .join("work")
             .join("4_merge")
             .join(format!("{story_id}.md"));
@@ -247,7 +247,7 @@ mod tests {
     async fn tool_move_story_to_merge_moves_file() {
         let tmp = tempfile::tempdir().unwrap();
         setup_git_repo_in(tmp.path());
-        let current_dir = tmp.path().join(".story_kit/work/2_current");
+        let current_dir = tmp.path().join(".storkit/work/2_current");
         std::fs::create_dir_all(&current_dir).unwrap();
         let story_file = current_dir.join("24_story_test.md");
         std::fs::write(&story_file, "---\nname: Test\n---\n").unwrap();
@@ -268,7 +268,7 @@ mod tests {
         // File should have been moved regardless of agent start outcome
         assert!(!story_file.exists(), "2_current file should be gone");
         assert!(
-            tmp.path().join(".story_kit/work/4_merge/24_story_test.md").exists(),
+            tmp.path().join(".storkit/work/4_merge/24_story_test.md").exists(),
             "4_merge file should exist"
         );
         // Result is either Ok (agent started) or Err (agent failed - acceptable in tests)