Step 17b: bytecode-compiled text-layout, WASM library import fix

- text-layout.sx added to WASM bytecode pipeline (9K compiled)
- Fix multi-list map calls (map-indexed + nth instead of map fn list1 list2)
- pretext-layout-lines and pretext-position-line moved to library exports
- Browser load-sxbc: handle VmSuspended for import, copy library exports
  to global_env after module load (define-library export fix)
- compile-modules.js: text-layout in SOURCE_MAP, FILES, and entry deps
- Island uses library functions (break-lines, pretext-layout-lines)
  instead of inlining — runs on bytecode VM when exports resolve

Known issue: define-library exports don't propagate to browser global env
yet. The load-sxbc import suspension handler resumes correctly but
bind_import_set doesn't fire. Needs deeper investigation into how the
WASM kernel's define-library registers exports vs how other libraries
(adapter-html, tw) make their exports available.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/text-layout.sx

@@ -13,6 +13,21 @@
 ;; Knuth-Plass optimal line breaking (DP over break candidates).
 ;; Liang's hyphenation (trie over character patterns).
 
+(define
+  pretext-position-line
+  (fn
+    (words widths gap-w)
+    (let
+      loop
+      ((i 0) (x 0) (acc (list)))
+      (if
+        (>= i (len words))
+        acc
+        (loop
+          (+ i 1)
+          (+ x (nth widths i) gap-w)
+          (append acc (list {:width (nth widths i) :x x :word (nth words i)})))))))
+
 (define-library
   (sx text-layout)
   (export
@@ -25,6 +40,8 @@
     break-lines-greedy
     position-line
     position-lines
+    pretext-position-line
+    pretext-layout-lines
     layout-paragraph
     make-hyphenation-trie
     find-hyphenation-points
@@ -131,7 +148,7 @@
               ((starts (cons 0 breaks)))
               (let
                 ((ends (append (rest starts) (list n))))
-                (map (fn (s e) (list s e)) starts ends)))))))
+                (map-indexed (fn (i s) (list s (nth ends i))) starts)))))))
     (define
       position-line
       (fn
@@ -266,7 +283,7 @@
             (let
               ((starts (cons 0 points))
                 (ends (append points (list (len word)))))
-              (map (fn (s e) (slice word s e)) starts ends))))))
+              (map-indexed (fn (i s) (slice word s (nth ends i))) starts))))))
     (define
       layout-paragraph
       (fn