feat: add portable Claude Code statusline kit

Replicating the cship-based statusline across machines meant manually
copying three files and hand-editing settings.json with per-user absolute
paths — error-prone and slow. Bundling the assets with an idempotent
installer that resolves the pwsh path at runtime and merges into an
existing settings.json makes rollout a single command per PC.

.gitignore

@@ -0,0 +1,3 @@
+# Local install artefacts / backups
+*.bak
+settings.json.bak