ci: run the web UI DOM test suites; fix two stale suites (#660)

A new "Web UI JS tests" job installs jsdom, starts the web interface in
emulator mode and runs test/js/run_all.js with REQUIRE_DOM=1, which makes a
DOM suite that can't run a failure rather than a silent skip. (The unit
suites were already covered through pytest.)

Two suites failed against main when run for real:
- test_tools_sections rendered the Tools partial without LEDEscape, which
  base.html's app-early.js defines; it now installs it in beforeParse, and
  supplies two sample Starlark apps (one id with a quote) when the server
  has none, instead of assuming a device with apps and Pixlet.
- test_store_dom assumed the live registry had at most 48 plugins; it now
  checks pagination whichever side of 48 it is.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/test.yml

@@ -8,7 +8,7 @@ on:
   # needs a re-run or didn't get created.
   workflow_dispatch:
 
-# Both jobs only check out the repo and run pytest.
+# The jobs only check out the repo and run the tests.
 permissions:
   contents: read
 
@@ -73,3 +73,42 @@ jobs:
             --cov=src --cov=web_interface \
             --cov-report=term \
             --cov-fail-under=52
+
+  js-tests:
+    name: Web UI JS tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-python@0b93645e9fea7318ecaed2b359559ac225c90a2b # v5.3.0
+        with:
+          python-version: "3.12"
+          cache: pip
+
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
+        with:
+          node-version: "22"
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt -r web_interface/requirements.txt
+          npm install --no-audit --no-fund --prefix test/js
+
+      # The DOM suites test the real server-rendered pages and API, so they
+      # need the web interface running. REQUIRE_DOM turns "couldn't reach it"
+      # into a failure instead of a silent skip.
+      - name: Start the web interface
+        run: |
+          EMULATOR=true python -c "from web_interface.app import app; app.run(host='127.0.0.1', port=5000, threaded=True)" > web.log 2>&1 &
+          for i in $(seq 60); do curl -sf -o /dev/null http://127.0.0.1:5000/ && exit 0; sleep 1; done
+          cat web.log
+          exit 1
+
+      - name: Run JS suites
+        env:
+          BASE: http://127.0.0.1:5000
+          REQUIRE_DOM: "1"
+        run: node test/js/run_all.js