feat: lifetime elision, tooling CI, registry, and LSP locals

Ship the QUALITY_PLAN stretch from ownership through ecosystem: C.1
lifetime elision (bootstrap + selfhost), bux fmt/test/doc CI hooks,
stdlib goldens, package registry (bux search/add), and LSP 0.4
position-sensitive locals with inferred let types. Full-tree format
pass plus Map/Set remove double-free fix.

registry/packages/greet/README.md

@@ -0,0 +1,15 @@
+# greet
+
+Demo package for the Bux registry (`config/registry.toml`).
+
+```bash
+bux add greet
+bux install
+```
+
+```bux
+func Main() -> int {
+    PrintLine(Greet_Hello("Bux"));
+    return 0;
+}
+```