Phases 15-16: SCI bootstrap, Janet interop, eval, lazy-cat, CLJS ported tests

- SCI bootstrap complete: all 9 SCI source files load (317 forms, 0 failures)
- prefer-method/remove-method/remove-all-methods promoted to special forms
- eval special form (interpreter + compiler) with eval-test.janet
- lazy-cat macro with structural equality tests in lazy-test.janet
- Janet-native interop via . special form on tables/structs:
  field access (. obj :key), method calls (. obj method args...)
  fn* form compilation support, .- reader sugar
  interop-test.janet with 7 test sections (14 assertions)
- New core bindings: with-meta, var-dynamic?, load-string
- ^:dynamic def handler, core-str nil handling, core-meta for with-meta
- 7 new CLJS ported test files: cljs-port-6 through -10, cljs-core-test, cljs-collections-test
- test-sci-runtime.janet verifies SCI namespaces/types/Var/IBox/IVar
- 317/317 tests pass, 0 failing scripts, 440+ assertions across 31 test files
- README updated with Janet interop documentation

test/phase5-test.janet

@@ -56,4 +56,14 @@
   (assert (ct-eval ctx "(try (rmtest {:k :a}) (catch Exception e true))") "removed method errors"))
 (print "  passed")
 
+# 27. remove-all-methods
+(print "27: remove-all-methods...")
+(let [ctx (init)]
+  (ct-eval ctx "(defmulti alltest :k)")
+  (ct-eval ctx "(defmethod alltest :a [_] 1)")
+  (ct-eval ctx "(defmethod alltest :b [_] 2)")
+  (ct-eval ctx "(remove-all-methods (var alltest))")
+  (assert (ct-eval ctx "(try (alltest {:k :a}) (catch Exception e true))") "all methods removed errors"))
+(print "  passed")
+
 (print "\nAll Phase 5 tests passed!")