macroexpand-first analyzer order; one macro path; defmacro/letfn fixes

The analyzer checked special forms before expanding macros, the reverse of the
canonical read -> macroexpand -> analyze order (Clojure/CLJS analyze-seq). Move
macroexpansion to the front of analyze-list. Knock-on fixes:

- letfn was both a (broken) macro expanding to let* AND a primitive special
  (analyze-letfn, proper letrec*). Macroexpand-first surfaced the macro, breaking
  mutual recursion; remove the macro, keep letfn a primitive.
- defmacro is now compiled by the analyzer (a :set-var-style :defmacro node that
  defs the expander fn via the fn macro — so destructuring arglists desugar — and
  marks the var a macro), so a non-top-level (when … (defmacro …)) works. The
  runtime spine's separate top-level defmacro interception is removed: one path.

SCI load 162 -> 202/218.

host/chez/run-sci.ss

@@ -1,11 +1,11 @@
 ;; run-sci.ss — SCI conformance: load borkdude/sci's own source (vendor/sci) through
 ;; joltc and require its forms to compile+eval. A real-world Clojure-compatibility
 ;; stress test. Pure Chez, no Janet. Floor-gated like the corpus: a regression below
-;; the floor (or the count today, 196/218) fails. Raise the floor as host gaps close
+;; the floor (or the count today, 202/218) fails. Raise the floor as host gaps close
 ;; (the tail is genuine gaps — set! on vars, some macro/def shapes).
 ;;
 ;;   chez --script host/chez/run-sci.ss
-;;   JOLT_SCI_FLOOR=N    override the floor (default 196)
+;;   JOLT_SCI_FLOOR=N    override the floor (default 202)
 ;;   SCI_VERBOSE=1       print each failing form's error
 (import (chezscheme))
 
@@ -74,7 +74,7 @@
   load-order)
 
 (printf "\nSCI load: ~a/~a forms ok (~a fail)\n" total-ok (+ total-ok total-fail) total-fail)
-(define floor (let ((s (getenv "JOLT_SCI_FLOOR"))) (if s (string->number s) 196)))
+(define floor (let ((s (getenv "JOLT_SCI_FLOOR"))) (if s (string->number s) 202)))
 (when (< total-ok floor)
   (printf "REGRESSION: ~a forms loaded < floor ~a\n" total-ok floor))
 (flush-output-port)