Simplify workflows

After renovating everything, it's evident that the ember-exam
sub-workflow can be inlined without any pesky duplication.

.github/workflows/_ember-exam.yml

@@ -1,27 +0,0 @@
-name: Ember Exam
-
-on:
-  workflow_call:
-    inputs:
-      partition:
-        required: true
-        type: number
-      split:
-        required: true
-        type: number
-    secrets:
-      PERCY_TOKEN:
-        required: true
-
-jobs:
-  exam:
-    runs-on: ubuntu-latest
-    timeout-minutes: 30
-    steps:
-      - uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab # v3.5.2
-      - name: yarn install
-        run: cd ui && yarn install --frozen-lockfile
-      - name: Ember tests
-        env:
-          PERCY_TOKEN: ${{ secrets.PERCY_TOKEN }}
-        run: cd ui && yarn exam:parallel -- --split=${{ inputs.split }} --partition=${{ inputs.partition }}

.github/workflows/test-ui.yml

@@ -39,38 +39,52 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    defaults:
+      run:
+        working-directory: ui
     steps:
       - uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab # v3.5.2
       - name: yarn install
-        run: cd ui && yarn install --frozen-lockfile
+        run: yarn install --frozen-lockfile
       - name: lint:js
-        run: cd ui && yarn run lint:js
+        run: yarn run lint:js
       - name: lint:hbs
-        run: cd ui && yarn run lint:hbs
+        run: yarn run lint:hbs
   tests:
     needs:
       - lint
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    defaults:
+      run:
+        working-directory: ui
     strategy:
       matrix:
         partition: [1, 2, 3, 4]
         split: [4]
-    uses: ./.github/workflows/_ember-exam.yml
-    with:
-      partition: ${{ matrix.partition }}
-      split: ${{ matrix.split }}
-    secrets: inherit
+    steps:
+      - uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab # v3.5.2
+      - name: yarn install
+        run: yarn install --frozen-lockfile
+      - name: ember exam
+        env:
+          PERCY_TOKEN: ${{ secrets.PERCY_TOKEN }}
+        run: yarn exam:parallel --split=${{ matrix.split }} --partition=${{ matrix.partition }}
   finalize:
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    defaults:
+      run:
+        working-directory: ui
     needs:
       - tests
     steps:
       - uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab # v3.5.2
       - name: yarn install
-        run: cd ui && yarn install --frozen-lockfile
+        run: yarn install --frozen-lockfile
       - name: finalize
         env:
           PERCY_TOKEN: ${{ secrets.PERCY_TOKEN }}
-        run: cd ui && yarn percy -- build:finalize
+        run: yarn percy build:finalize
 permissions:
   contents: read