Remove the Swagger try-it page

It shipped 1.77 MB of vendored assets to every site - swagger-ui-bundle.min.js
alone is larger than Redoc - in order to provide an Execute button that only the
development config ever enabled. Production config had it off, testing had it
off hard, and when off the routes were never bound at all. The staticdocs
directory drops from 2.9 MB to 1.1 MB, and there is one fewer vendored
dependency to track for licences and advisories.

What replaces it: an agent has the MCP server's shopdb_call, and a human has
Redoc for reading plus the 324 harvested examples in the spec for a curl that is
mostly copy-paste. The read-only page was always the one that mattered.

The tests this leaves behind are the interesting part. That file was named for
try-it but half of it proved things about the page that stays, above all that
nothing it loads comes from the internet, which is what a CDN reference costs on
an air-gapped box. Those are kept and the file is renamed for what it covers.

Pointing the air-gap test at redoc.standalone.js immediately failed: the bundle
still carried a trailing sourceMappingURL for a .map that was never vendored,
so every devtools open was a guaranteed 404 with no internet to fall back on.
That was visible in a browser console and nobody had chased it, because the test
had only ever been parametrised over the two Swagger files. The pragma is gone
and the assertion now checks the TRAILING pragma specifically: Redoc's own code
contains that string three more times, in a data: URI it assembles and in a
worker blob, and a blunt "not in body" assertion fails on correct code.

A first attempt to strip it with a line-anchored pattern removed 507 KB, because
the bundle is minified onto long lines. Hence the anchored, byte-exact removal
and the assertion that can tell a directive from source.

docs/API-REFERENCE.md

@@ -25,7 +25,6 @@ generated; nothing of that kind belongs on this page.
 | `GET /api/docs` | The reference, rendered with Redoc. The bundle is vendored in the image, so it renders with no network - which is the only reason it is usable on an air-gapped site. |
 | `GET /api/docs/openapi.json` | The raw OpenAPI 3.1 spec. Also tracked as `docs/openapi.json`, so it can be read from a checkout without running anything; regenerate with `scripts/gen_openapi.py` after any API change. |
 | `GET /api/docs/llms.txt` | The short version, for a machine caller. Also [llms.txt](llms.txt) in this corpus. |
-| `GET /api/docs/try` | Swagger UI over the same spec, where Execute sends a real request as whoever is signed in on that browser. Off by default (`API_DOCS_TRYIT_ENABLED`) and not something a production site turns on without deciding to. |
 
 [llms.txt](llms.txt) is not a second spec. It is the orientation a caller needs
 before the spec is useful: the response envelope, how authentication is