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-parser.sx

@@ -649,6 +649,64 @@
       (assert= "reset" (nth ast 1))
       (assert= 0 (len (nth ast 2))))))
 
+(defsuite
+  "hs-parse-render"
+  (deftest
+    "render component"
+    (let
+      ((ast (hs-compile "render ~card")))
+      (assert= (quote render) (first ast))
+      (assert= "~card" (nth ast 1))
+      (assert= 0 (len (nth ast 2)))))
+  (deftest
+    "render with kwargs"
+    (let
+      ((ast (hs-compile "render ~card :title 'Hello'")))
+      (assert= "~card" (nth ast 1))
+      (let
+        ((kw (nth ast 2)))
+        (assert= "title" (first kw))
+        (assert= "Hello" (nth kw 1)))))
+  (deftest
+    "render into target"
+    (let
+      ((ast (hs-compile "render ~card :title 'Hi' into #box")))
+      (assert= "into" (nth ast 3))
+      (assert= (quote query) (first (nth ast 4)))))
+  (deftest
+    "component token in expression"
+    (let
+      ((ast (hs-compile "set x to ~myComp")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote component) (first val))
+        (assert= "~myComp" (nth val 1))))))
+
+(defsuite
+  "hs-parse-sx-eval"
+  (deftest
+    "eval with parens extracts raw SX"
+    (let
+      ((ast (hs-compile "set x to eval (+ 1 2)")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote sx-eval) (first val))
+        (assert= "(+ 1 2)" (nth val 1)))))
+  (deftest
+    "eval with string fallback"
+    (let
+      ((ast (hs-compile "eval '(log 42)'")))
+      (assert= (quote sx-eval) (first ast))
+      (assert= "(log 42)" (nth ast 1))))
+  (deftest
+    "eval nested parens"
+    (let
+      ((ast (hs-compile "set x to eval (map (fn (x) (+ x 1)) items)")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote sx-eval) (first val))
+        (assert= "(map (fn (x) (+ x 1)) items)" (nth val 1))))))
+
 (defsuite
   "hs-parse-every-modifier"
   (deftest