HS: tell uses beingTold implicit target, preserves me (+3 tests)

tell now rebinds beingTold/you/yourself without overwriting me.
Parser implicit targets use beingTold; handler wrapper seeds beingTold=me.
Fixes: attributes refer to the thing being told, does not overwrite me,
your symbol represents the thing being told.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/hyperscript/integration.sx

@@ -19,6 +19,7 @@
       (define
         reserved
         (list
+          (quote beingTold)
           (quote me)
           (quote it)
           (quote event)
@@ -65,7 +66,10 @@
                   (list (quote me))
                   (list
                     (quote let)
-                    (list (list (quote it) nil) (list (quote event) nil))
+                    (list
+                      (list (quote beingTold) (quote me))
+                      (list (quote it) nil)
+                      (list (quote event) nil))
                     guarded))))))))))
 
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