fix(quality): the E2E front-controller gate blocked every app without an index route - #145

… an index route

The Playwright job proved the `php -S` front controller was routing by
requesting `/apps/<app-name>/` and failing on 404. That conflated two
independent properties:

  1. does the front controller route pretty URLs — a CI concern, and
  2. does THIS app have an index route — an app design choice.

A settings-only app has no `/` route and no navigation entry, so
`/apps/<app>/` is a correct Nextcloud 404. The gate read that as a broken
router, exited 1 before a single spec ran, and printed an error naming the
router. nldesign#206 hit exactly this: 31 specs that navigate to
`/settings/admin/theming` never executed, and the failure text pointed at
`php -S`.

That the two are separable is measurable on that PR: on run 30859016722
(job 91836768845) the same URL returned **500**, not 404 — index.php had
executed and thrown on a missing cross-app class. Same router, same
request, different status. So a 404 there is Nextcloud saying "no such
route", not `php -S` saying "no such directory index".

The probe now uses `/apps/files/`, which is the right shape for what is
being proven. `php -S` 404s a path resolving to a real directory with no
index.php inside it; that is the entire failure mode the router exists to
fix. `apps/files` is shipped, always enabled, has no index.php, and its
route always resolves (302 to /login unauthenticated).

Measured on a fixture with and without the router — note that the obvious
alternatives are DEAD probes, because a router-less `php -S` already
serves them from the root index.php:

                      no router    with router
    /apps/files/          404          200      <- discriminates
    /apps/<app>/          404          200      <- discriminates, but 404
                                                   is also legitimate
    /login                200          200      <- proves nothing
    /nonexistent/         200          200      <- proves nothing

`/apps/<app-name>/` is still requested and its status still printed, as a
`::notice::` rather than a gate — a page app that lost its route and a
settings-only app that never had one look identical from here, and only
the spec run can tell them apart.