test: fold cljs ports into spec; add exceptions spec + gap coverage

Mine the cljs port batteries into the spec layer and delete them (their behavior
is covered by spec; the unique functions they exercised are now specced).
Removed test/integration/ports/ entirely.

New/expanded spec coverage from the mining:
- spec/exceptions-spec: try/catch/finally, throw, ex-info/ex-message/ex-data/ex-cause
- doto, pr-str, keyword/symbol constructors, atom?, dynamic var binding

Two rare edges filed (jolt-...): rethrow of a caught ex-info re-wraps it; var-set
on a dynamic var inside binding no-ops. Core try/catch/ex-info and binding work.

Test layout is now spec (22 files, ~677 cases) / integration / unit / support.
conformance 218/218, jpm test green.

test/spec/strings-spec.janet

@@ -11,6 +11,8 @@
   ["subs from"          "\"bc\""     "(subs \"abc\" 1)"]
   ["subs range"         "\"b\""      "(subs \"abc\" 1 2)"]
   ["string? true"       "true"       "(string? \"x\")"]
+  ["pr-str vector"      "\"[1 2 3]\"" "(pr-str [1 2 3])"]
+  ["pr-str quotes str"  "\"\\\"hi\\\"\"" "(pr-str \"hi\")"]
   ["seq of string"      "[\\a \\b]"  "(seq \"ab\")"])
 
 (defspec "clojure.string"