fix: declare click_page_item on the wasm-surface ratchet

`web/tests/bundle/wasm_surface.test.js` pins the "handful of calls" the page
reaches the client through, and its own comment says a new one has to come and
say so. This is that. The reason it belongs on the list rather than above the
seam: the page holds no `Basis`, so `SetPageSelection` cannot be composed there.

It needs a built `web/pkg`, so it lives in `web/tests/bundle/` and is outside
the `web/tests/*.test.js` glob the brief's gate names — it only ran in CI.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FC2jVn8Au7E9JPkw6bwXXH

web/tests/bundle/wasm_surface.test.js

@@ -75,6 +75,9 @@ test("the page still reaches the client through a handful of calls", () => {
       "click_category",
       "click_cell",
       "click_formula",
+      // improvise-rw6l: picking an item off a page axis. The page holds no
+      // `Basis`, so composing `SetPageSelection` cannot happen above this.
+      "click_page_item",
       "click_tile",
       "click_view",
       "on_frame",