selfhost: expand Decl to 256 fields, fix unary precedence, add discard/var parsing, fix diag buffer overflow

- ast.bux: Decl expanded with field0..field255, variant0..7, param0..8
- parser.bux: add parserParseUnary for correct unary precedence; handle tkDiscard statements; allow var without initializer (matching bootstrap); add diagCount bounds check in parserEmitDiag
- hir.bux: HirParam changed to pointers
- hir_lower.bux: full field chains for struct lowering
- c_backend.bux: hardened -> vs . field access; null checks in CBE_GetExprTypeName
- cli.bux: add -lcrypto to linker

src/hir.bux

@@ -79,15 +79,15 @@ struct HirParam {
 struct HirFunc {
     name: String;
     paramCount: int;
-    param0: HirParam;
-    param1: HirParam;
-    param2: HirParam;
-    param3: HirParam;
-    param4: HirParam;
-    param5: HirParam;
-    param6: HirParam;
-    param7: HirParam;
-    param8: HirParam;
+    param0: *HirParam;
+    param1: *HirParam;
+    param2: *HirParam;
+    param3: *HirParam;
+    param4: *HirParam;
+    param5: *HirParam;
+    param6: *HirParam;
+    param7: *HirParam;
+    param8: *HirParam;
     retTypeKind: int;
     retTypeName: String;
     body: *HirNode;