Contract fixes from the baseline audit; every residual suite failure traced

Auditing the remaining cts baseline for R7 exposed real contract gaps hiding
among the model residue — all fixed to reference behavior:

- stale no-ratio-era stubs: numerator/denominator now work over jolt's exact
  rationals (non-ratio is the Ratio cast failure); rational? includes decimals
- casts and pending: peek/pop demand an IPersistentStack (pop nil is nil),
  realized? demands an IPending (a plain list/range throws), transient demands
  an editable COLLECTION (non-colls throw; the RFC 0003 sorted/list/seq
  superset keeps the copy-on-write fallback), empty on a plain record throws
- nil and empties: (nth nil i) is nil, (nth nil i d) is d, a nil index is NPE,
  keys/vals of anything empty are nil, (conj nil) is nil
- lookups: contains? on a string is index-only (other keys IAE), get on an
  array is lenient (nth still throws), a VECTOR invocation has nth semantics
  (([1 2] 5) throws — call position and jolt-invoke both)
- into only transients editable collections; a PersistentQueue/sorted target
  folds through conj (RT's IEditableCollection split)
- numbers: number?/num accept BigDecimal, quot/rem throw on an Infinite/NaN
  quotient, even?/odd? demand integers
- ordering: keywords compare namespace-first with nil first (Symbol.compareTo)
- misc: run! honors reduced, eval self-evaluates non-form values, intern
  demands an existing namespace, counted? excludes strings, seqable? includes
  arrays, shuffle rejects maps, sort-by rejects a collection comparator,
  when-let demands one binding pair, case*/deftype*/letfn*/reify*/& are
  special symbols

Two mis-certified corpus rows fixed (they threw on the JVM too and hid in the
tolerated bucket): a raw \d string escape and duplicate literal map keys.

SPEC.md gains the baseline-traceability section: every one of the 146
remaining suite failures maps to a documented divergence (integer-box,
no-single-float, RFC 0003 transients, seq/chunking model, stm-refs,
parse-uuid strictness, vec-array adoption). cts baseline 5955 -> 6042 pass,
5 errors, 30 namespaces. 9 JVM-certified corpus rows.

test/chez/cts-known-failures.txt

@@ -5,55 +5,29 @@ clojure.core-test.abs 1 0
 clojure.core-test.add-watch 0 1
 clojure.core-test.bigint 6 0
 clojure.core-test.bit-set 1 0
-clojure.core-test.compare 1 0
-clojure.core-test.conj 1 0
-clojure.core-test.contains-qmark 3 0
-clojure.core-test.counted-qmark 1 0
 clojure.core-test.dec 1 0
-clojure.core-test.denominator 0 3
 clojure.core-test.double-qmark 3 0
-clojure.core-test.empty 1 0
 clojure.core-test.eq 2 0
-clojure.core-test.eval 0 3
-clojure.core-test.even-qmark 1 0
 clojure.core-test.float 1 0
-clojure.core-test.get 0 1
 clojure.core-test.inc 1 0
 clojure.core-test.int-qmark 3 0
-clojure.core-test.intern 2 0
-clojure.core-test.keys 0 4
-clojure.core-test.lazy-seq 3 0
+clojure.core-test.lazy-seq 1 2
 clojure.core-test.minus 2 0
-clojure.core-test.mod 23 0
+clojure.core-test.mod 18 0
 clojure.core-test.neg-int-qmark 1 0
 clojure.core-test.not-eq 3 0
-clojure.core-test.nth 0 1
-clojure.core-test.num 2 1
-clojure.core-test.number-qmark 3 0
-clojure.core-test.numerator 0 3
-clojure.core-test.odd-qmark 1 0
+clojure.core-test.num 2 0
 clojure.core-test.parse-uuid 3 0
-clojure.core-test.peek 2 0
+clojure.core-test.peek 1 0
 clojure.core-test.plus 11 0
 clojure.core-test.plus-squote 11 0
-clojure.core-test.pop 0 1
 clojure.core-test.pos-int-qmark 1 0
-clojure.core-test.quot 30 0
+clojure.core-test.quot 25 0
 clojure.core-test.rand-nth 0 1
-clojure.core-test.rational-qmark 3 0
-clojure.core-test.realized-qmark 3 0
-clojure.core-test.rem 21 0
+clojure.core-test.realized-qmark 1 0
+clojure.core-test.rem 16 0
 clojure.core-test.remove-watch 0 1
-clojure.core-test.run-bang 1 0
-clojure.core-test.select-keys 2 0
-clojure.core-test.seqable-qmark 1 0
-clojure.core-test.shuffle 1 0
-clojure.core-test.sort-by 2 0
-clojure.core-test.special-symbol-qmark 4 0
 clojure.core-test.star 13 0
 clojure.core-test.star-squote 13 0
-clojure.core-test.transient 23 0
-clojure.core-test.update 1 0
-clojure.core-test.vals 0 3
+clojure.core-test.transient 4 0
 clojure.core-test.vec 1 0
-clojure.core-test.when-let 1 0