Auto-resolve ::keywords; honor clojure.edn reader opts

The reader dropped the namespace on ::kw (read ::foo as :foo), so auto-resolved
keywords never matched their qualified form — code that round-trips them (spec
keys, aero's :aero.core/* expansion keys) silently broke. Resolve ::name against
the current ns and ::alias/name through the alias table, as Clojure does. The
runtime loader reads form-by-form with the ns set after the ns form; the
cross-compile reads all forms up front, so ei-emit-ns*/ei-emit-ns-records set the
ns before reading.

clojure.edn/read over a reader discarded its opts map — :readers/:default/:eof
were ignored, so a custom :default never saw the tag. Route the reader arity
through read-string so opts apply, and pass the tag to :default as a symbol (not
the internal :#name keyword), matching Clojure.

Seed re-minted (the ::halt transducer key in clojure.core now reads as
:clojure.core/halt). Corpus gains ::-keyword rows; the unit case that asserted the
old ns-dropping behavior now asserts the qualified result.

host/chez/reader.ss

@@ -451,11 +451,19 @@
 
 ;; --- keyword ----------------------------------------------------------------
 (define (rdr-read-keyword s i end)       ; i points just past the leading ':'
-  ;; ::kw auto-resolves; drop the ns, so skip a second ':'
-  (let ((i (if (and (< i end) (char=? (string-ref s i) #\:)) (+ i 1) i)))
-    (let-values (((tok j) (rdr-read-token s i end)))
-      (let-values (((ns name) (rdr-sym-parts tok)))
-        (values (keyword ns name) j)))))
+  ;; ::kw is auto-resolved against the current ns: ::name -> current-ns/name,
+  ;; ::alias/name -> the alias's target ns / name (Clojure's reader semantics).
+  (let ((auto? (and (< i end) (char=? (string-ref s i) #\:))))
+    (let ((i (if auto? (+ i 1) i)))
+      (let-values (((tok j) (rdr-read-token s i end)))
+        (let-values (((ns name) (rdr-sym-parts tok)))
+          (if auto?
+              (let* ((cur (chez-current-ns))
+                     (rns (if (string? ns)
+                              (let ((a (chez-resolve-alias cur ns))) (if a a ns))
+                              cur)))
+                (values (keyword rns name) j))
+              (values (keyword ns name) j)))))))
 
 ;; --- the main dispatch ------------------------------------------------------
 ;; Returns (values form j). form is rdr-eof at end-of-input or at an unconsumed