fix(web): the stamp guard names every missing stamp, not the first (improvise-x4wv)

`stamped` exited on the first failure, so breaking two substitutions named
app.js and never reached worker.js -- and the comment ("names itself when it is
the one missing") read as though it did not. It fails safe, which is why it was
filed rather than fixed in PR #47; the code is fixed rather than the comment
because the diagnostic is paid for in wasm-pack rebuilds, the slowest loop in
this repo.

Each stamp is still verified on its own -- the property PR #24's finding bought
-- but `stamped` records and a gate after the four calls fails the build.
Proved by injection both ways: two broken sedi patterns now name both files and
exit 1, and deleting the gate prints both failures while exiting 0, which is
the check-that-does-not-check the comment now warns about.

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

web/assemble.sh

@@ -73,18 +73,31 @@ sedi "s|'improvise_worker_server_bg\.wasm'|'improvise_worker_server_bg.wasm?v=${
 # three failed substitutions could still produce a "successful" assembly under
 # `set -e` (found by Copilot on PR #24). These checks are the only guard
 # against the generated glue changing shape, so each stamped reference is
-# verified on its own and names itself when it is the one missing.
+# verified on its own and names itself when it is missing.
+#
+# `stamped` RECORDS rather than exits, and the gate below is what fails the
+# build. Exiting on the first failure named one file and never reached the
+# rest, so a shape change that broke two stamps cost two wasm-pack rebuilds to
+# diagnose -- the slowest loop in this repo (improvise-x4wv). The gate is the
+# whole guard: without it every failure prints and the assembly succeeds, which
+# is the check-that-does-not-check this whole file is full of fixes for.
+missing=""
 stamped() {
-  grep -q "$2" "$1" || {
+  if grep -q "$2" "$1"; then
+    grep -n "$2" "$1"
+  else
     echo "assemble: $1 is missing the cache-bust stamp: $2" >&2
-    exit 1
+    missing="${missing} $1"
-  }
+  fi
-  grep -n "$2" "$1"
 }
 stamped "$app/app.js" "pkg/improvise_wasm_client.js?v=${token}"
 stamped "$app/worker.js" "worker-pkg/improvise_worker_server.js?v=${token}"
 stamped "$app/pkg/improvise_wasm_client.js" "improvise_wasm_client_bg.wasm?v=${token}"
 stamped "$app/worker-pkg/improvise_worker_server.js" "improvise_worker_server_bg.wasm?v=${token}"
+test -z "$missing" || {
+  echo "assemble: refusing to ship; unstamped:${missing}" >&2
+  exit 1
+}
 
 # Every relative import the two entry points make must have been copied. The
 # cp list above is a second answer to "what ships", and a missing sibling is a