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).

src/jolt/clojure/sci/lang_stubs.clj

@@ -0,0 +1,32 @@
+; Minimal SCI type stubs for Jolt bootstrap
+; Provides the deftype definitions that SCI's Clojure source references
+; before the full SCI runtime is loaded.
+
+; Protocol stubs for SCI's type system
+(defprotocol IBox (setVal [this v]) (getVal [this]))
+(defprotocol HasName (getName [this]))
+(defprotocol IVar (bindRoot [this v]) (getRawRoot [this]) (toSymbol [this])
+  (isMacro [this]) (setThreadBound [this v]) (unbind [this]) (hasRoot [this]))
+(defprotocol DynVar (dynamic? [this]))
+(defprotocol IReified (getInterfaces [this]) (getMethods [this])
+  (getProtocols [this]) (getFields [this]))
+
+; Unbound sentinel for vars
+(deftype SciUnbound [the-var])
+
+; Core SCI types — keep minimal for bootstrap
+(deftype Namespace [name mappings aliases imports])
+(deftype Var [root name meta macro dynamic ns])
+
+; Store stub (sci.ctx-store provides a global context atom)
+(def ctx-store (atom nil))
+
+; Macro helpers from sci.impl.macros
+(defn deftime [& body] nil)
+(defn usetime [& body] (eval (first body)))
+(defmacro ? [& args]
+  (if (contains? &env (quote &env))
+    (let [form (first args)]
+      (if (= :clj (first form))
+        (second form)
+        (if (= :cljs (first form)) nil)))))

src/jolt/core.janet

@@ -1334,6 +1334,7 @@
     "IllegalStateException" core-IllegalStateException
     "definterface" core-definterface
     "defrecord" core-defrecord
+    "comment" core-comment
     "resolve" core-resolve
     "update" core-update
     "copy-core-var" core-copy-core-var

src/jolt/types.janet

@@ -219,7 +219,7 @@
 (defn ns?
   "Check if x is a Jolt Namespace."
   [x]
-  (and (struct? x) (= :jolt/namespace (x :jolt/type))))
+  (and (or (struct? x) (table? x)) (= :jolt/namespace (x :jolt/type))))
 
 (defn ns-name
   "Return the name symbol of a namespace."