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.

src/source_location.bux

@@ -1,13 +1,13 @@
 // source_location.bux — Source position tracking
 module SourceLocation {
 
-struct SourceLocation {
-    line: uint32;
-    column: uint32;
-    offset: uint32;
-}
+    struct SourceLocation {
+        line: uint32;
+        column: uint32;
+        offset: uint32;
+    }
 
-func SourceLocation_New(line: uint32, column: uint32, offset: uint32) -> SourceLocation {
-    return SourceLocation { line: line, column: column, offset: offset };
-}
+    func SourceLocation_New(line: uint32, column: uint32, offset: uint32) -> SourceLocation {
+        return SourceLocation { line: line, column: column, offset: offset };
+    }
 }