HS: contains/matches ignoring case support — 425→426

- Parser: contains/matches with ignoring case modifier
- Compiler: contains-ignore-case? → hs-contains-ignore-case?
- Compiler: matches-ignore-case? → hs-matches-ignore-case?
- Runtime: downcase-based case-insensitive contains/matches

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

lib/hyperscript/parser.sx

@@ -520,9 +520,27 @@
                   (match-kw "with")
                   (list (quote ends-with?) left (parse-expr))))
               ((and (= typ "keyword") (= val "matches"))
-                (do (adv!) (list (quote matches?) left (parse-expr))))
+                (do
+                  (adv!)
+                  (let
+                    ((right (parse-expr)))
+                    (if
+                      (match-kw "ignoring")
+                      (do
+                        (match-kw "case")
+                        (list (quote matches-ignore-case?) left right))
+                      (list (quote matches?) left right)))))
               ((and (= typ "keyword") (= val "contains"))
-                (do (adv!) (list (quote contains?) left (parse-expr))))
+                (do
+                  (adv!)
+                  (let
+                    ((right (parse-expr)))
+                    (if
+                      (match-kw "ignoring")
+                      (do
+                        (match-kw "case")
+                        (list (quote contains-ignore-case?) left right))
+                      (list (quote contains?) left right)))))
               ((and (= typ "keyword") (= val "as"))
                 (do
                   (adv!)