Propagate source position through macroexpansion

hc-expand-1 now carries the macro call form's :line/:column onto the top of a
list expansion that has none of its own (merged under any meta the macro set),
so errors and stack traces in macro-generated code point at the call site —
Clojure parity. The analyze recursion re-expands inner macros, so each level's
top form picks it up, matching the reference compiler. (meta (macroexpand-1
'(when x y))) now reports the call-site line.

A direct-link fn defined through a user macro (build-app's defguarded) registers
with a real line, so build-smoke's trace assertion covers macro-defined fns.

Runtime .ss (host-contract.ss) — no re-mint; selfhost holds.

Phase 3's optional items are deferred: :line-in-ex-data has no clean consumer
(it would pollute ex-data, break = and printing, and positions already surface
via the trace + top-level location), and Chez source-object emission is a large
backend change the jv$-name registry already sidesteps.

test/chez/build-app/src/app/util.clj

@@ -5,9 +5,13 @@
   (str/upper-case (str s "!")))
 
 ;; A two-deep non-tail call chain that throws — exercises native stack traces in a
-;; direct-link build (build-smoke runs -main with a --boom sentinel arg).
-(defn deep-boom [x]
-  (assert (number? x) "needs a number")
+;; direct-link build (build-smoke runs -main with a --boom sentinel arg). deep-boom
+;; is defined through a USER macro: its source registration only gets a real line
+;; if the reader position survives macroexpansion (so the trace frame maps).
+(defmacro defguarded [name args & body]
+  `(defn ~name ~args (assert (number? ~(first args)) "needs a number") ~@body))
+
+(defguarded deep-boom [x]
   (* x 2))
 
 (defn mid-boom [x]