landing2.html IFC import is broken as packaged: import_worker.js and web-ifc are absent from deploy/

[chertsa]

deploy/landing2.html looks like the only page wired for IFC import at this commit —
deploy/dev/index.html has neither #import-zone nor #import-file-input, and
deploy/dev/landing.html has the input but never loads import.js, so nothing is bound to
it. And landing2's import cannot run:

• it loads sandbox/import_db_builder.js, which constructs the worker relative to
  itself → sandbox/import_worker.js?v=7. There is no import_worker.js anywhere under
  deploy/ — the only copy is deploy/dev/import_worker.js.
• the worker then loads web-ifc from sandbox/lib/. There is no deploy/sandbox/lib/;
  web-ifc lives at deploy/dev/lib/.

Observed on a pristine clone: the page loads, the picker accepts an IFC, then the import
dies with net::ERR_FAILED on sandbox/import_worker.js. Serve that file and it dies again
on sandbox/lib/web-ifc-api-iife.js. Serve both and the import completes normally
(§IMPORT_SAVED … elements=60) — so the pipeline is fine and only the packaging is wrong.
Same class as issue 1's sandbox/ asset note, but this one breaks the feature.

Worth knowing: the four 07-import-ifc specs all assert DOM presence only — drop zone
exists, input accepts .ifc, no console errors, unsupported-format message — so none of
them performs a real import, and a completely non-functional import path stays green.

Suggested fix. Ship import_worker.js and lib/ at deploy/ beside landing2.html
(or have the GH_DEPLOY.md assembly place them), and add one spec that imports a real IFC
and asserts an element count.