Hyperscript: focus command, diagnostic test output, blur keyword

Parser/compiler/runtime for focus command. Tokenizer: focus, blur,
precedes, follows, ignoring, case keywords. Test spec: per-test
failure output for diagnosis.

374/831 (45%)

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

lib/hyperscript/tokenizer.sx

@@ -170,7 +170,9 @@
     "precedes"
     "follows"
     "ignoring"
-    "case"))
+    "case"
+    "focus"
+    "blur"))
 
 (define hs-keyword? (fn (word) (some (fn (k) (= k word)) hs-keywords)))