feat: stdlib daily APIs, macro tt/type paste, riscv64 cross smoke

Sessions 83–87: grow Array/Map/String/Test ergonomics; delimiter-balanced
and juxta :tt macros plus $t:type fragments; expression-level $(…),* in
templates; selfhost slice lits; riscv64/aarch64 cross smoke helper and
freestanding docs. Null-safe CBE type names and String_StartsWith.

bootstrap/sema.nim

@@ -1921,9 +1921,9 @@ proc checkExpr*(sema: var Sema, expr: Expr, scope: Scope): Type =
     # Should have been expanded before analyze; leftover is a compiler bug
     sema.emitError(expr.loc, "unexpanded macro call '" & expr.exprMacroName & "!'")
     return makeUnknown()
-  of ekMacroStmt, ekMacroPat:
+  of ekMacroStmt, ekMacroPat, ekMacroTt, ekMacroRep, ekMacroType:
     # Expand-only wrappers; must not reach type-checking
-    sema.emitError(expr.loc, "internal: unexpanded macro stmt/pat fragment")
+    sema.emitError(expr.loc, "internal: unexpanded macro fragment")
     return makeUnknown()
   of ekClosure:
     let savedRetType = sema.currentRetType