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.

examples/borrow.bux

@@ -1,8 +1,8 @@
 // borrow.bux — Test explicit borrow expressions
 
 struct Point {
-	x: int;
-	y: int;
+    x: int;
+    y: int;
 }
 
 // NOT @[Checked] — borrow keyword available everywhere