Phase 11: Fix pre-existing failures — 316/317 passing

- types.janet: ns? now accepts both structs and tables
  (defensive for namespace-like tables created via @{...})
- core.janet: wire comment macro into core-bindings
  (was in core-macro-names but missing from core-bindings)
- sci/lang_stubs.clj: minimal SCI type stubs for bootstrap
  (IBox, HasName, IVar, DynVar protocols, SciUnbound/Var/Namespace deftypes)
- test-load-sci.janet: load stubs before SCI source files,
  removed broken preprocessor

Before: 315 ok, 2 fail (SciVar + array/buffer)
After:  316 ok, 1 fail (only deftype in lang.cljc remains)

The remaining failure is lang.cljc's SciVar deftype with #?@ inserts
for JVM/CLJS-specific protocol implementations — a known limitation
for Phase 15 (SCI bootstrap).

test/test-load-sci.janet

@@ -5,6 +5,20 @@
 
 (def ctx (init))
 
+(printf "Loading SCI stubs...\n")
+(defn load-stubs [ctx filepath]
+  (var s (slurp filepath))
+  (var count 0)
+  (while (> (length (string/trim s)) 0)
+    (def [form rest] (parse-next s))
+    (set s rest)
+    (++ count)
+    (when (not (nil? form))
+      (eval-form ctx @{} form)))
+  (printf "  Loaded %d stub forms\n" count))
+
+(load-stubs ctx "src/jolt/clojure/sci/lang_stubs.clj")
+
 (defn load-file [ctx path]
   (var s (slurp path))
   (var count 0)