test(spec): macros, reader, host-interop, namespaces — fix def-doc, resolve, %&

Final spec areas. Bugs caught and fixed:
- (def name docstring value) used the docstring as the value; now the 3-arg
  docstring form binds the value and records :doc meta
- resolve was a nil stub; now a special form resolving a symbol to its var
  (nil if unresolved). Added find-ns (non-creating lookup) and ns-name.
- in-ns didn't evaluate its arg, so (in-ns 'foo) failed; now evaluates it per
  Clojure (the integration test's unquoted form updated to the quoted idiom)
- #(... %& ...) built %& as a positional param instead of a & rest param;
  now emits (fn* [... & gen] ...) so %& captures the rest

Full public-API spec layer now in place. conformance 218/218, jpm test green.

test/spec/host-interop-spec.janet

@@ -0,0 +1,17 @@
+# Specification: host (Janet) interop — the `.` forms and jolt.interop.
+(use ../support/harness)
+
+(defspec "interop / dot forms"
+  ["method call"        "\"v=41\""
+   "(. {:value 41 :describe (fn [self] (str \"v=\" (:value self)))} describe)"]
+  ["method with args"   "\"Hello Alice\""
+   "(. {:greet (fn [self n] (str \"Hello \" n))} greet \"Alice\")"]
+  ["field access .-"    "41"        "(.-value {:value 41})"]
+  ["dot field keyword"  "41"        "(. {:value 41} :value)"])
+
+(defspec "interop / jolt.interop"
+  ["janet-type quoted list" ":array" "(do (require (quote [jolt.interop :as j])) (j/janet-type (quote (1 2))))"]
+  ["janet-type list"    ":array"    "(do (require (quote [jolt.interop :as j])) (j/janet-type (list 1 2)))"]
+  ["janet-type string"  ":string"   "(do (require (quote [jolt.interop :as j])) (j/janet-type \"x\"))"]
+  ["janet-type number"  ":number"   "(do (require (quote [jolt.interop :as j])) (j/janet-type 1))"]
+  ["janet-type keyword" ":keyword"  "(do (require (quote [jolt.interop :as j])) (j/janet-type :a))"])