Fix Pretext island: library functions inside define-library begin block

Root cause: sx_insert_near placed break-lines-greedy, pretext-position-line,
pretext-layout-lines OUTSIDE the define-library begin block. The bytecode
compiler only compiles forms inside begin as STORE_GLOBAL — forms outside
are invisible to the browser VM.

Fix: moved all function definitions inside (begin ...) of (define-library).
Bytecode now includes all 17 functions (11K compiled, was 9K).

Browser load-sxbc: simplified VmSuspended handling — just catch and
continue, since STORE_GLOBAL ops already ran before the import OP_PERFORM.
sync_vm_to_env copies them to global_env.

Island now calls break-lines and pretext-layout-lines from bytecode-compiled
library — runs on VM, not CEK interpreter.

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

lib/text-layout.sx

@@ -13,21 +13,6 @@
 ;; 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
@@ -149,6 +134,32 @@
               (let
                 ((ends (append (rest starts) (list n))))
                 (map-indexed (fn (i s) (list s (nth ends i))) starts)))))))
+    (define
+      break-lines-greedy
+      (fn
+        (widths space-width max-width)
+        (let
+          ((n (len widths)))
+          (if
+            (= n 0)
+            (list)
+            (let
+              ((lines (list)) (start 0) (used 0))
+              (for-each
+                (fn
+                  (i)
+                  (let
+                    ((w (nth widths i))
+                      (needed (if (= i start) w (+ used space-width w))))
+                    (if
+                      (and (> needed max-width) (not (= i start)))
+                      (do
+                        (set! lines (append lines (list (list start i))))
+                        (set! start i)
+                        (set! used w))
+                      (set! used needed))))
+                (range n))
+              (append lines (list (list start n))))))))
     (define
       position-line
       (fn
@@ -181,6 +192,45 @@
                   (line-widths (slice widths start end)))
                 (position-line line-words line-widths space-width x0 y))))
           line-ranges)))
+    (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
+      pretext-layout-lines
+      (fn
+        (words widths ranges space-width max-width line-height)
+        (let
+          ((n-lines (len ranges)))
+          (map
+            (fn
+              (line-idx)
+              (let
+                ((range (nth ranges line-idx))
+                  (y (* line-idx line-height)))
+                (let
+                  ((start (first range)) (end (nth range 1)))
+                  (let
+                    ((lw (slice words start end))
+                      (lwid (slice widths start end)))
+                    (let
+                      ((total-w (reduce + 0 lwid))
+                        (n-gaps (max 1 (- (len lw) 1)))
+                        (is-last (= line-idx (- n-lines 1))))
+                      (let
+                        ((gap (if is-last space-width (/ (- max-width total-w) n-gaps))))
+                        {:y y :words (pretext-position-line lw lwid gap)}))))))
+            (range n-lines)))))
     (define
       make-hyphenation-trie
       (fn
@@ -327,31 +377,4 @@
             (lh (or line-height 1.4)))
           (layout-paragraph words f s w lh))))))
 
-(define
-  break-lines-greedy
-  (fn
-    (widths space-width max-width)
-    (let
-      ((n (len widths)))
-      (if
-        (= n 0)
-        (list)
-        (let
-          ((lines (list)) (start 0) (used 0))
-          (for-each
-            (fn
-              (i)
-              (let
-                ((w (nth widths i))
-                  (needed (if (= i start) w (+ used space-width w))))
-                (if
-                  (and (> needed max-width) (not (= i start)))
-                  (do
-                    (set! lines (append lines (list (list start i))))
-                    (set! start i)
-                    (set! used w))
-                  (set! used needed))))
-            (range n))
-          (append lines (list (list start n))))))))
-
 (import (sx text-layout))