build(web): rebuild plugin bundles before the browser lane

test:web ran build:web alone, which does not rebuild UI plugin client
bundles. Plugin CSS reaches the browser through packages/client/*/lib/
client.js, not apps/web/dist, so a changed *.module.css served its
previous bundle: the run exercised stale CSS and a removed declaration
still passed. That is how I first mistook a valid gutter test for a
vacuous one.

Root build already covers packages/*/*, so running it first is enough;
check-all already ordered build before build:web, so CI was never
exposed. Only the local script was, which is where a stale-bundle pass is
most likely to be believed.

Verified against the situation it fixes: mutate the source, rebuild the
bundle, restore the source, and the artifact is left without the
declaration while the source has it. Under the old script the run tested
that artifact; under the new one the artifact is rebuilt first (grep goes
0 to 1) and the scrollbar spec passes. The nine failing web files are the
pre-existing aria-golden set from f2c004524, unchanged by this.

package.json

@@ -29,7 +29,7 @@
     "test:snapshot:record": "DSH_SNAPSHOT=record vitest run --config vitest.snapshot.config.ts --update",
     "test:snapshot:refresh": "DSH_SNAPSHOT=refresh vitest run --config vitest.snapshot.config.ts",
     "migrate:packed-session-fixtures": "tsx scripts/migrate-packed-session-fixtures.ts",
-    "test:web": "npm run build:web && vitest run --config vitest.web.config.ts",
+    "test:web": "npm run build && npm run build:web && vitest run --config vitest.web.config.ts",
     "test:gui": "vitest run packages/client packages/host",
     "check:all": "tsx scripts/run-gates.ts check-all",
     "check:ci": "tsx scripts/run-gates.ts ci-primary",