TypeCheck Frontend (#2394)

We recently had an error that would've been caught by type checking in the frontend (see #2393). This PR implements type checking so that future errors will be caught.

Additionally, this PR contains miscellaneous frontend cleanup that's tangentially related to type-checking.

.github/workflows/build.yml

@@ -91,18 +91,34 @@ jobs:
   #         ./gradlew build
   #         ./gradlew clean
 
+  typecheck-client:
+    name: "Typecheck Client"
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+      - name: Install pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: 24
+          cache: pnpm
+          cache-dependency-path: photon-client/pnpm-lock.yaml
+      - name: Typecheck Client
+        working-directory: photon-client
+        run: |
+          pnpm install --frozen-lockfile
+          pnpm type-check
   playwright-tests:
     name: "Playwright E2E tests"
     runs-on: ubuntu-24.04
     needs: [validation]
     steps:
-      # Checkout code.
       - name: Checkout code
         uses: actions/checkout@v6
-        with:
-          fetch-depth: 0
-      - name: Fetch tags
-        run: git fetch --tags --force
       - uses: actions/setup-java@v5
         with:
           java-version: 25
@@ -136,7 +152,6 @@ jobs:
     runs-on: ubuntu-24.04
     needs: [validation]
     steps:
-      # Checkout code.
       - name: Checkout code
         uses: actions/checkout@v6
         with: