Fix general gaps the hiccup suite shook out

Six correctness fixes, each a general gap (not hiccup-specific):

- deftype is not a map. jolt treated every deftype instance as a map
  (map?/record?/seqable over its fields); in Clojure only a defrecord is
  map-like, a bare deftype is an opaque object. defrecord now marks its type;
  map?/record?/coll?/seq/empty? gate on it, while a deftype implementing a
  collection interface still dispatches through its methods.

- cross-ns extend-protocol on an imported deftype. register-method built the
  type tag from the *calling* ns + bare name, so (extend-protocol P Raw …) in
  one ns missed a Raw value defined in another. A simple-name index resolves
  the bare name to the type's real tag (local ns still wins).

- str vs print. str of a collection is its readable form (nested strings
  quoted: (str ["x"]) => ["x"]); print leaves them raw. jolt defined print
  as str, conflating the two. Split via a __print1 seam.

- clojure.test thrown? now honors the exception hierarchy (instance?), so
  (thrown? IllegalArgumentException …) matches an ArityException subclass.

- java.net.URI is value-equal (= and hash by string form).

- clojure.walk/macroexpand-all was missing; an unresolved qualified var made
  the analyzer report "Unknown class walk".

deftype/defrecord + print are seed sources, re-minted. hiccup 365->381 of its
own suite; the rest are charset-encoding / var-meta niches.

host/chez/post-prelude.ss

@@ -95,10 +95,10 @@
 ;; chunked-seq? is true for a vector's seq (a real chunked-seq); the overlay's
 ;; always-false stub loaded over the host fn, so re-assert it.
 (def-var! "clojure.core" "chunked-seq?" na-chunked-seq?)
-;; record? is a host type check (jrec?), not the overlay's (some? (get x
-;; :jolt/deftype)) — the get-trick invokes a sorted-map's comparator on
-;; :jolt/deftype and throws. Matches the JVM (instance? IRecord).
-(def-var! "clojure.core" "record?" (lambda (x) (jrec? x)))
+;; record? is a host type check — true only for a defrecord, not a bare deftype
+;; (jrec-record?), matching the JVM (instance? IRecord). The overlay's
+;; (some? (get x :jolt/deftype)) get-trick would invoke a sorted-map comparator.
+(def-var! "clojure.core" "record?" (lambda (x) (jrec-record? x)))
 
 ;; read / read+string over a HOST reader jhost (java.io StringReader/PushbackReader):
 ;; the overlay's IReader protocol only covers the reify map-reader, so a (read