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.

tests/error_golden/elision_multi_input/src/Main.bux

@@ -0,0 +1,9 @@
+@[Checked]
+func Pick(a: &int, b: &int) -> &int {
+    return a;
+}
+
+@[Checked]
+func Main() -> int {
+    return 0;
+}