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>

sx/sx/pretext-client.sx

@@ -1,4 +1,5 @@
 ;; Pretext island — client-side text layout with live controls
+;; Uses bytecode-compiled break-lines from text-layout library.
 
 (defisland
   ~pretext-demo/live
@@ -13,51 +14,9 @@
       (canvas (host-call doc "createElement" "canvas"))
       (ctx (host-call canvas "getContext" "2d")))
     (let
-      ((mw (fn (word sz) (do (host-set! ctx "font" (str sz "px 'Pretext Serif', DejaVu Serif, serif")) (host-get (host-call ctx "measureText" word) "width"))))
-        (sw-fn
-          (fn
-            (widths sw from to)
-            (let
-              loop
-              ((k from) (total 0))
-              (if
-                (>= k to)
-                (+ total (* (max 0 (- (- to from) 1)) sw))
-                (loop (+ k 1) (+ total (nth widths k)))))))
-        (brk-greedy
-          (fn
-            (widths sw mx)
-            (let
-              ((n (len widths)) (lines (list)) (st 0) (us 0))
-              (for-each
-                (fn
-                  (i)
-                  (let
-                    ((w (nth widths i)) (nd (if (= i st) w (+ us sw w))))
-                    (if
-                      (and (> nd mx) (not (= i st)))
-                      (do
-                        (set! lines (append lines (list (list st i))))
-                        (set! st i)
-                        (set! us w))
-                      (set! us nd))))
-                (range n))
-              (append lines (list (list st n))))))
-        (pos-line
-          (fn
-            (lw lwid gap)
-            (let
-              loop
-              ((i 0) (x 0) (acc (list)))
-              (if
-                (>= i (len lw))
-                acc
-                (loop
-                  (+ i 1)
-                  (+ x (nth lwid i) gap)
-                  (append acc (list {:x x :word (nth lw i)}))))))))
+      ((mw (fn (word sz) (do (host-set! ctx "font" (str sz "px 'Pretext Serif', DejaVu Serif, serif")) (host-get (host-call ctx "measureText" word) "width")))))
       (let
-        ((layout (computed (fn () (let ((sz (deref font-size)) (mxw (deref max-w)) (opt (deref use-optimal))) (let ((widths (map (fn (w) (mw w sz)) words)) (spw (mw " " sz)) (lh (* sz 1.5))) (let ((ranges (brk-greedy widths spw mxw)) (result (list))) (for-each (fn (li) (let ((rng (nth ranges li)) (y (* li lh))) (let ((s (first rng)) (e (nth rng 1))) (let ((n-line (- e s)) (lw (list)) (lwid (list))) (for-each (fn (k) (append! lw (nth words (+ s k))) (append! lwid (nth widths (+ s k)))) (range n-line)) (let ((tw (reduce + 0 lwid)) (ng (max 1 (- n-line 1))) (il (= li (- (len ranges) 1)))) (let ((gap (if il spw (/ (- mxw tw) ng)))) (append! result {:y y :words (pos-line lw lwid gap)}))))))) (range (len ranges))) result)))))))
+        ((layout (computed (fn () (let ((sz (deref font-size)) (mxw (deref max-w)) (opt (deref use-optimal))) (let ((widths (map (fn (w) (mw w sz)) words)) (spw (mw " " sz)) (lh (* sz 1.5))) (let ((ranges (if opt (break-lines widths spw mxw) (break-lines-greedy widths spw mxw)))) (pretext-layout-lines words widths ranges spw mxw lh))))))))
         (div
           (~tw :tokens "space-y-4")
           (div