Chez Phase 2 (inc R): . / .-field dot-form desugar (jolt-kuic)

The analyzer lowers the `.` special form (. target member arg*) and the
.-field field-access head to a :host-call instead of leaving them
uncompilable. Janet behaviour is unchanged — its back end punts :host-call
to the interpreter, which re-runs the original `.` form via eval-dot.

The Chez back end routes a non-shimmed :host-call through
record-method-dispatch, extended by a new host/chez/dot-forms.ss with the
arms dispatch-member covers but the record/string base did not, mirroring
src/jolt/interop/collections.janet precedence:

  - collection interop first (count/seq/nth/get/valAt/containsKey on a
    vector/map/set), so (. {:count 9} count) is the entry count like the seed
  - field access for a "-name" member (records and maps)
  - the seed's universal object-methods (getMessage/getCause/toString/
    hashCode/equals) on a non-record map, winning over a field lookup
  - non-record map member: a stored fn is a method called with self, else
    the field value

Raw seqs are excluded from coll interop — the seed's behaviour there is
representation-dependent (plain (seq v) vs a lazy-seq) and a normalized cseq
can't mirror it. Also added getMessage/getLocalizedMessage/equals to the
string method surface so a thrown string / Exception. ctor (which keeps the
message string) answers .getMessage.

Parity 2134 -> 2150, 0 new divergences. New test/chez/_dotform.janet 26/26;
emit-test 331/331.

host/chez/rt.ss

@@ -277,3 +277,8 @@
 ;; record-method-dispatch (records.ss) and reuses natives-str helpers (str-trim,
 ;; ascii-string-down, re-split, str-split-drop-trailing) + the regex-t accessors.
 (load "host/chez/host-static.ss")
+
+;; generic dot-form dispatch (jolt-kuic): field access + map/vector member access
+;; for the `.` / `.-field` desugar. Loads after host-static.ss so it wraps every
+;; record-method-dispatch arm (jhost/number/regex/jrec/string) and falls through.
+(load "host/chez/dot-forms.ss")