HS: ask/answer + prompt/confirm mock (+4 tests)

Wire up the `ask` and `answer` commands end-to-end:

- tokenizer.sx: register `ask` and `answer` as hs-keywords.

- parser.sx: cmd-kw? gains both; parse-cmd dispatches to new
  parse-ask-cmd (emits `(ask MSG)`) and parse-answer-cmd, which
  reads `answer MSG [with YES or NO]`. The with/or pair reads
  yes/no via parse-atom — parse-expr would collapse
  `"Yes" or "No"` into `(or "Yes" "No")` before match-kw "or"
  could fire. The no-`with` form emits `(answer-alert MSG)`.

- compiler.sx: three new cond branches (ask, answer, answer-alert)
  compile to a let that binds __hs-a, sets `the-result` and `it`,
  and returns the value — so `then put it into ...` works.

- runtime.sx: hs-ask / hs-answer / hs-answer-alert call
  window.prompt / confirm / alert via host-call + host-global.

- tests/hs-run-filtered.js: test-name-keyed globalThis.{alert,
  confirm,prompt}; __currentHsTestName is updated before each
  test. Host-set! for innerHTML/textContent now coerces JS
  null → "null" (browser behaviour) so `prompt → null` →
  `put it into #out` renders literal text "null", which the
  fourth test depends on.

Suite hs-upstream-askAnswer: 1/5 -> 5/5.
Smoke 0-195: 166/195 -> 170/195.

lib/hyperscript/compiler.sx

@@ -1757,6 +1757,39 @@
                 (list (quote hs-settle) (quote me)))
               ((= head (quote go))
                 (list (quote hs-navigate!) (hs-to-sx (nth ast 1))))
+              ((= head (quote ask))
+                (let
+                  ((val (list (quote hs-ask) (hs-to-sx (nth ast 1)))))
+                  (list
+                    (quote let)
+                    (list (list (quote __hs-a) val))
+                    (list
+                      (quote begin)
+                      (list (quote set!) (quote the-result) (quote __hs-a))
+                      (list (quote set!) (quote it) (quote __hs-a))
+                      (quote __hs-a)))))
+              ((= head (quote answer))
+                (let
+                  ((val (list (quote hs-answer) (hs-to-sx (nth ast 1)) (hs-to-sx (nth ast 2)) (hs-to-sx (nth ast 3)))))
+                  (list
+                    (quote let)
+                    (list (list (quote __hs-a) val))
+                    (list
+                      (quote begin)
+                      (list (quote set!) (quote the-result) (quote __hs-a))
+                      (list (quote set!) (quote it) (quote __hs-a))
+                      (quote __hs-a)))))
+              ((= head (quote answer-alert))
+                (let
+                  ((val (list (quote hs-answer-alert) (hs-to-sx (nth ast 1)))))
+                  (list
+                    (quote let)
+                    (list (list (quote __hs-a) val))
+                    (list
+                      (quote begin)
+                      (list (quote set!) (quote the-result) (quote __hs-a))
+                      (list (quote set!) (quote it) (quote __hs-a))
+                      (quote __hs-a)))))
               ((= head (quote __get-cmd))
                 (let
                   ((val (hs-to-sx (nth ast 1))))