Compiler research (#10)

adds self-hosted compiler is functionally:
 
- The default compile path is the portable pipeline using jolt.analyzer (Clojure) → host-neutral IR → backend.janet.
- The analyzer is itself Clojure, compiled by jolt for true self-hosting.
- bootstrap-fixpoint passes (stage1 == stage2 == stage3): rebuilding the compiler on its own output.
- clojure.core is now self-hosted in the overlay.
- Stateful forms (defmacro/ns/deftype/defmulti/require/in-ns) are interpreted by design.

test/spec/strings-spec.janet

@@ -48,3 +48,8 @@
   ["subs end past len"  :throws    "(subs \"abcde\" 1 6)"]
   ["subs nil start"     :throws    "(subs \"abcde\" nil 2)"]
   ["subs on nil"        :throws    "(subs nil 1 2)"])
+
+(defspec "string / namespace-munge"
+  ["hyphens to underscores" "\"a_b_c\"" "(namespace-munge \"a-b-c\")"]
+  ["from a symbol"          "\"foo_bar\"" "(namespace-munge (quote foo-bar))"]
+  ["no hyphens unchanged"   "\"ok\""    "(namespace-munge \"ok\")"])