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/mod.rs

@@ -45,7 +45,7 @@ pub fn resolve_port() -> u16 {
 }
 
 pub fn write_port_file(dir: &Path, port: u16) -> Option<PathBuf> {
-    let path = dir.join(".story_kit_port");
+    let path = dir.join(".storkit_port");
     std::fs::write(&path, port.to_string()).ok()?;
     Some(path)
 }