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/bux.toml

@@ -0,0 +1,7 @@
+[Package]
+Name    = "elision_multi_input"
+Version = "0.1.0"
+Type    = "bin"
+
+[Build]
+Output = "Bin"

tests/error_golden/elision_multi_input/expected.err

@@ -0,0 +1,7 @@
+error: type errors in project
+error: lifetime elision failed: return type needs an explicit lifetime (multiple input references); e.g. func F<'a>(a: &'a T, b: &'a U) -> &'a T
+  --> FILE:2:1
+    |
+ 2 | func Pick(a: &int, b: &int) -> &int {
+    | ^^^^
+   = help: add an explicit lifetime, e.g. func F<'a>(x: &'a T, y: &'a U) -> &'a T

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;
+}