HS: cluster 11/33 followups (+2 tests)

Three orthogonal fixes that pick up tests now unblocked by earlier
cluster-34 (count filters) and cluster-35 (hs-method-call fallback) work:

(1) parser.sx parse-hide-cmd / parse-show-cmd — added `on` to the keyword
list that signals an implicit-`me` target. Without this, `on click 1
hide on click 2 show` silently parsed as `(hide nil)` because parse-expr
greedily started consuming `on` and returned nil. With the bail-out,
hide/show default to me when the next token is `on` (a sibling feature).

(2) runtime.sx hs-method-call fallback — when method isn't a built-in
collection op, look up obj[method] via host-get; if it's an SX-callable
(lambda) use apply, but if it's a JS-native function (e.g. cookies.clear
on the cookies Proxy) dispatch via `(apply host-call (cons obj (cons
method args)))` so the JS native receives the args correctly. SX
callable? returns false for JS-native function values, hence the split.

(3) generator hs-cleanup! — wrapped body in begin (fn body evaluates
only the last expression) and reset two pieces of mutable global runtime
state between tests: hs-set-default-hide-strategy! nil and
hs-set-log-all! false. The prior `can set default to custom strategy`
test (cluster 11) was leaking _hs-default-hide-strategy to subsequent
tests, breaking `hide element then show element retains original
display` because hs-hide-one! resolved its "display" strategy through
the leaked override.

Also added cluster-33 hand-roll for `basic clear cookie values work`
(uses the new method-call fallback to dispatch cookies.clear via
host-call).

hs-upstream-hide: 15/16 → 16/16. hs-upstream-expressions/cookies: 3/5
→ 4/5. Smoke 0-195 unchanged at 172/195.

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

spec/tests/test-hyperscript-behavioral.sx

@@ -20,7 +20,11 @@
 
 (define hs-cleanup!
   (fn ()
-    (dom-set-inner-html (dom-body) "")))
+    (begin
+      (dom-set-inner-html (dom-body) "")
+      ;; Reset global runtime state that prior tests may have set.
+      (hs-set-default-hide-strategy! nil)
+      (hs-set-log-all! false))))
 
 ;; Evaluate a hyperscript expression and return either the expression
 ;; value or `it` (whichever is non-nil). Multi-statement scripts that
@@ -4929,7 +4933,11 @@
 ;; ── expressions/cookies (5 tests) ──
 (defsuite "hs-upstream-expressions/cookies"
   (deftest "basic clear cookie values work"
-    (error "SKIP (untranslated): basic clear cookie values work"))
+    (hs-cleanup!)
+    (eval-hs "set cookies.foo to 'bar'")
+    (assert= (eval-hs "cookies.foo") "bar")
+    (eval-hs "call cookies.clear('foo')")
+    (assert (nil? (eval-hs "cookies.foo"))))
   (deftest "basic set cookie values work"
     (hs-cleanup!)
     (assert (nil? (eval-hs "cookies.foo")))