Nothing covered the intersection #1859 fell through. `smoke:web:app` drives
the App path but against the repo build tree; `pack:verify` runs against the
installed tarball but only asserted the sandbox proxy page *exists*. So a
packaging regression that ships the file present-but-unreachable — a rename
with a stale reader, a wrong position relative to clients/web/build, a future
"files"/.npmignore edit — passes both.
Extract the drive-the-App-flow half of the smoke into
scripts/lib/mcp-app-flow.mjs and call it from both, rather than copying it:
the deep-link shape is the part that rots silently, and a drifted link fails
as an opaque timeout rather than a mismatch. pack:verify then drives
connect -> open app -> data-app-status="ready" in headless Chromium against
the installed `--web` boot it already starts.
The client under test comes from the install; the App test server stays a
repo fixture.
Also isolates pack:verify's `--web` catalog (the #1977 treatment the smokes
already have). Untidy while the step only did `GET /`; the App deep link
persists a server row, which would make it destructive and non-deterministic
against the developer's real ~/.mcp-inspector/mcp.json.
Unit tests cover what neither consumer can check itself — both CSRF gates and
the appArgs encoding on the deep link, and driveAppFlow's failure branches
against a stand-in page, all dead code from a happy-path smoke's view.
Verified: pack:verify passes end to end against the real tarball, and fails
at the new step alone when sandbox-controller.ts is pointed at a renamed
proxy page (the tarball and on-disk assertions both still pass — the exact
gap this closes).
Signed-off-by: cliffhall <cliff@futurescale.com>