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;
+}
+```

registry/packages/greet/bux.toml

@@ -0,0 +1,9 @@
+[Package]
+Name    = "greet"
+Version = "0.1.1"
+Type    = "lib"
+Authors = ["Bux Core"]
+License = "MIT"
+
+[Build]
+Output = "Lib"

registry/packages/greet/src/Greet.bux

@@ -0,0 +1,14 @@
+// greet — demo registry package (E.1)
+module Greet {
+
+    /// Return a greeting for `name`.
+    func Greet_Hello(name: String) -> String {
+        return String_Concat("Hello, ", String_Concat(name, "!"));
+    }
+
+    /// Return the package version string.
+    func Greet_Version() -> String {
+        return "0.1.1";
+    }
+
+}