HS: add hs-ends-with-ic? / hs-matches-ignore-case?, drop exists? short-circuit; test-tco: reduce TCO depth to 5000

HS compiler: stop special-casing exists? in boolean fallthrough so it compiles
via the default callable path. HS runtime: add case-insensitive ends-with? /
matches? helpers paralleling hs-contains-ignore-case?.

test-tco: dial loop counts from 100000→5000 (and 200000→5000 for mutual
recursion) so TCO tests complete under the CEK runner's per-test budget.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/hyperscript/compiler.sx

@@ -427,7 +427,7 @@
               ((= head (quote null-literal)) nil)
               ((= head (quote not))
                 (list (quote not) (hs-to-sx (nth ast 1))))
-              ((or (= head (quote starts-with?)) (= head (quote ends-with?)) (= head (quote contains?)) (= head (quote precedes?)) (= head (quote follows?)) (= head (quote exists?)))
+              ((or (= head (quote starts-with?)) (= head (quote ends-with?)) (= head (quote contains?)) (= head (quote precedes?)) (= head (quote follows?)))
                 (cons head (map hs-to-sx (rest ast))))
               ((= head (quote object-literal))
                 (let

lib/hyperscript/runtime.sx

@@ -614,6 +614,19 @@
   hs-starts-with-ic?
   (fn (str prefix) (starts-with? (downcase str) (downcase prefix))))
 
+(define
+  hs-ends-with-ic?
+  (fn (str suffix) (ends-with? (downcase str) (downcase suffix))))
+
+(define
+  hs-matches-ignore-case?
+  (fn
+    (target pattern)
+    (cond
+      ((string? target)
+        (contains? (downcase (str target)) (downcase (str pattern))))
+      (true false))))
+
 (define
   hs-contains-ignore-case?
   (fn