Chez Phase 1 (increment 3a): persistent collections on the Chez RT

Broaden the Scheme back end past the numeric/functional subset to vectors,
maps, and sets. host/chez/collections.ss adds a copy-on-write persistent
vector and a bitmap HAMT (the structure 0c measured self-hostable) backing
both maps and sets, keyed by jolt-hash and compared by jolt=. emit.janet
emits :vector/:map/:set literals to the rt constructors and lowers the leaf
ops (conj/get/nth/count/assoc/dissoc/contains?/empty?/peek/pop) via the
native-ops path, with a per-op arity gate.

Also: keyword/map literals in fn position lower to jolt-get ((:k m), ({:k v} k));
arity-1 comparisons emit the vacuous jolt truth (Scheme < rejects a non-number
even at arity 1); count returns a flonum and vector indices coerce from flonum,
both consequences of the all-double number model; values.ss = / hash and the
rt printer learn collections (maps/sets render in HAMT order, so the probe
compares unordered values via =, not printed form).

Subset parity 182 -> 433/436 compiled cases (2219/2655 out of subset), 0 new
divergences. The 3 known divergences are dynamic IFn dispatch (a keyword/vector
held in a local, called as a fn) — deferred to the IFn/protocol increment and
allowlisted in the probe. emit-test 31/31, full run-tests green (125 files).

host/chez/values.ss

@@ -56,6 +56,8 @@
     ((and (char? a) (char? b)) (char=? a b))
     ((and (string? a) (string? b)) (string=? a b))
     ((and (boolean? a) (boolean? b)) (eq? a b))
+    ;; collections: forward to collections.ss (loaded after this file by rt.ss).
+    ((and (jolt-coll? a) (jolt-coll? b)) (jolt-coll=? a b))
     (else (eq? a b))))
 (define (jolt= a . rest)
   (let loop ((a a) (rest rest))
@@ -78,4 +80,5 @@
     ((string? x) (string-hash x))
     ((char? x) (char->integer x))
     ((boolean? x) (if x 1 2))
+    ((jolt-coll? x) (jolt-coll-hash x))   ; forward to collections.ss
     (else (equal-hash x))))