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>

lib/hyperscript/tokenizer.sx

@@ -137,7 +137,9 @@
     "install"
     "measure"
     "behavior"
-    "called"))
+    "called"
+    "render"
+    "eval"))
 
 (define hs-keyword? (fn (word) (some (fn (k) (= k word)) hs-keywords)))
 
@@ -408,6 +410,14 @@
                   (hs-advance! 1)
                   (hs-emit! "attr" (read-ident pos) start)
                   (scan!))
+                (and
+                  (= ch "~")
+                  (< (+ pos 1) src-len)
+                  (hs-letter? (hs-peek 1)))
+                (do
+                  (hs-advance! 1)
+                  (hs-emit! "component" (str "~" (read-ident pos)) start)
+                  (scan!))
                 (and
                   (= ch "*")
                   (< (+ pos 1) src-len)