[saas-e2e] reduce disk IO and webpack overhead (#36997)

* [monorepo] reduce writes from chrome in cypress

Chrome puts its shared memory in /dev/shm, and docker's default 64MB is far
too small for it - which is why Cypress passes --disable-dev-shm-usage,
spilling those segments to files on the container's writable layer instead.
Under one spec that is a few hundred MB of write-then-delete churn; under the
CI fan-out it was most of the disk bandwidth on the whole box.

So every service built from dockerfiles/cypress gets shm_size 1gb and every
cypress config drops the flag again: the SaaS e2e service, web's CI and local
component-test services plus its standalone cypress one, and server-ce's e2e
and native cypress services. Both e2e-open variants inherit the setting
through `extends`; the native one is a service of its own, and would be left
running Chrome against 64MB once the flag is gone.

* [monorepo] adopt cypress-pnp-reporter

Materializing the reporter packages copied 267 packages / 3779 files
(59MB) into /tmp on every container start, once per spec. Resolving them
through PnP inside Cypress's Electron process instead drops that to
zero: the entrypoint shell went from 55.6MB of write_bytes to 0.

* [web] serve built assets from a prepared buffer between builds

Serving a chunk cost ~2ms whatever its size, and an editor page pulls ~144
of them, so webpack-dev-server burned 2-3 cores through an e2e run purely
answering requests for output that had not changed since the last build.

It is not bytes: cutting the bundle 2.6x with a cheaper devtool moved CPU
by 8%, and an empty 304 cost nearly as much as the full body. It is the
per-request work - reading the asset out of the in-memory filesystem and
re-hashing the whole body for a strong ETag, on every request.

Three things a build does that this has to respect, each found by tracing
the hooks rather than by reading them:

- `done` fires twice per build, for the compilation and for the manifest,
  both with the same hash. A flag would have been cleared by the second
  while the first was still running, so the gate is a counter.
- An incremental `done` reports only the assets it rewrote - 16, not 630 -
  so asset names accumulate. Resetting them on `invalid` left the
  manifest's two behind and nothing was served from here again.
- webpack-dev-middleware holds requests during a rebuild. This sits in
  front of it, so it steps aside for that window and drops the cache when
  a rebuild starts. Whether a response can be kept is then decided as it
  ends rather than as it began: an epoch bumped on `invalid` names the
  build its bytes were read from, and only a response from the current
  build with no rebuild in flight is stored. A rebuild starting
  mid-response can no longer write the previous build's bytes in behind
  the cache being dropped, which eviction by asset name could not catch
  anyway - an incremental build does not name the assets it left alone.

Measured on the editor entrypoint, 16 concurrent clients:
0.26-0.31s -> 0.045-0.050s of webpack CPU per page load, and 0.0455s
immediately after a rebuild. Same chunk graph, byte-identical output.

GitOrigin-RevId: 08b4ab2d665414069bc01b4763dd64faa9b4e5cb

services/web/package.json

@@ -40,9 +40,8 @@
     "type-check:backend": "tsc -p tsconfig.backend.json --noEmit",
     "extract-translations": "i18next-scanner",
     "convert-themes": "node frontend/js/features/source-editor/themes/scripts/convert.js",
-    "materialize-reporter": "node ../../bin/shared/materialize-cypress-reporter.js /tmp/cypress-reporter",
-    "cypress:open-ct": "yarn run materialize-reporter && OVERLEAF_CONFIG=$(pwd)/config/settings.webpack.js cypress open --component",
-    "cypress:run-ct": "yarn run materialize-reporter && OVERLEAF_CONFIG=$(pwd)/config/settings.webpack.js cypress run --component --browser chrome",
+    "cypress:open-ct": "OVERLEAF_CONFIG=$(pwd)/config/settings.webpack.js cypress open --component",
+    "cypress:run-ct": "OVERLEAF_CONFIG=$(pwd)/config/settings.webpack.js cypress run --component --browser chrome",
     "cypress:docker:open-ct": "USER_UID=$(id -u) USER_GID=$(id -g) docker compose -f docker-compose.cypress.yml run --rm cypress yarn run cypress:open-ct",
     "cypress:docker:run-ct": "USER_UID=$(id -u) USER_GID=$(id -g) docker compose -f docker-compose.cypress.yml run --rm cypress yarn run cypress:run-ct --browser chrome",
     "lezer-latex:generate": "node scripts/lezer-latex/generate.mjs",
@@ -228,6 +227,7 @@
     "@lezer/lr": "1.4.7",
     "@lezer/markdown": "1.6.3",
     "@overleaf/codemirror-tree-view": "^0.1.3",
+    "@overleaf/cypress-pnp-reporter": "workspace:*",
     "@overleaf/dictionaries": "https://github.com/overleaf/dictionaries/archive/refs/tags/v0.0.3.tar.gz",
     "@overleaf/eslint-plugin": "workspace:*",
     "@overleaf/ranges-tracker": "workspace:*",
@@ -332,7 +332,6 @@
     "csv-parse": "^6.2.1",
     "csv-stringify": "^6.7.0",
     "cypress": "15.20.1",
-    "cypress-multi-reporters": "^2.0.5",
     "cypress-plugin-tab": "^1.0.5",
     "d3": "^3.5.16",
     "daterangepicker": "2.1.27",