Step 18 (part 7): Extensions — render components + SX escape

Two hyperscript extensions beyond stock:

render ~component :key val [into|before|after target]
  Tokenizer: ~ + ident → component token type
  Parser: render command with kwargs and optional position
  Compiler: emits (render-to-html ~comp :key val) or
            (hs-put! (render-to-html ...) pos target)
  Bridges hyperscript flow to SX component rendering

eval (sx-expression) — SX escape hatch
  Inside eval (...), content is SX syntax (not hyperscript)
  Parser: collect-sx-source extracts balanced parens from raw source
  Compiler: sx-parse at compile time, inlines AST directly
  Result: SX runs in handler scope — hyperscript variables visible!
  Also supports string form: eval '(+ 1 2)' for backward compat

  set name to "Giles"
  set greeting to eval (str "Hello " name)  -- name is visible!

16 new tests (parser + compiler + integration).
3127/3127 full build, zero regressions.

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

spec/tests/test-hyperscript-runtime.sx

@@ -125,4 +125,22 @@
       ((sx (hs-to-sx-from-source "def add(a, b) return a end")))
       (assert= (quote define) (first sx))
       (assert= (quote add) (nth sx 1))
-      (assert= (quote fn) (first (nth sx 2))))))
+      (assert= (quote fn) (first (nth sx 2))))))
+
+(defsuite
+  "hs-handler-extensions"
+  (deftest
+    "render compiles to render-to-html"
+    (let
+      ((sx (hs-to-sx-from-source "render ~badge :label 'New'")))
+      (assert= (quote render-to-html) (first sx))
+      (assert= (quote ~badge) (nth sx 1))))
+  (deftest
+    "eval inlines SX with variable access"
+    (let
+      ((h (hs-handler "set x to 10 then set y to eval (+ x 5)")))
+      (h "el")
+      (assert= 15 y)))
+  (deftest
+    "eval as command in handler"
+    (let ((h (hs-handler "eval (set! z 99)"))) (h "el") (assert= 99 z))))