ci(labs): run WASM persistence regression test in wasm-smoke-test job

Wires labs/tests/test_wasm_persistence.py into CI per @Shashank-Tripathi-07's
request, so #1985's silent IndexedDB data-loss bug (and the Python
name-mangling bug that caused it) can't regress unnoticed.

PLAYWRIGHT_BROWSERS_PATH is pinned to a fixed, HOME-independent
location on both the install and test steps, since
labs/tests/conftest.py redirects $HOME for test isolation, which
would otherwise make Playwright look for its browser cache in the
wrong place once pytest runs.

Kept --override-ini="addopts=" on the pytest invocation: the root
pyproject.toml's addopts requires --cov=book/tools, but pytest-cov
isn't installed in this job, which is the exact failure I hit locally
before adding this override.

Author: aadityansha06

.github/workflows/labs-validate-dev.yml

@@ -1,3 +1,4 @@
+
 name: '🔮 Labs · ✅ Validate (Dev)'
 
 # =============================================================================
@@ -279,14 +280,41 @@ jobs:
       # enabled and Pyodide threading works. A lab is considered healthy when
       # a marimo DOM signal (tab, cell, or island) attaches within 180s.
       - name: 🎭 Install Playwright + Chromium
+        env:
+          # Fixed, HOME-independent location. labs/tests/conftest.py
+          # redirects $HOME for test isolation (so lab tests don't touch a
+          # real ~/.mlsys), which would otherwise make Playwright look for
+          # its browser cache in the wrong place once pytest runs. See the
+          # WASM persistence regression test step below.
+          PLAYWRIGHT_BROWSERS_PATH: ${{ github.workspace }}/.pw-browsers
         run: |
           pip install playwright
           python3 -m playwright install --with-deps chromium
 
       - name: 🌐 Browser smoke test (real Chromium + Pyodide)
+        env:
+          PLAYWRIGHT_BROWSERS_PATH: ${{ github.workspace }}/.pw-browsers
         run: |
           python3 labs/tests/browser_smoke.py --labs-dir /tmp/wasm-smoke
 
+      # =====================================================================
+      # WASM/IndexedDB persistence regression test (#1985 / PR #1988)
+      # =====================================================================
+      # DesignLedger.save_async() previously reported success while
+      # silently failing to persist to IndexedDB, due to a Python
+      # name-mangling bug (globalThis.__mlsys_temp_state written inside the
+      # class body was rewritten to globalThis._DesignLedger__mlsys_temp_state,
+      # desyncing it from the plain name the embedded JS read). Mocked unit
+      # tests (mlsysim/tests/test_state.py) can't catch this class of bug
+      # since they replace save_async() entirely. This runs the real
+      # save_async() against real Pyodide + real IndexedDB in headless
+      # Chromium and reads the write back through a separate connection.
+      - name: 🧪 WASM persistence regression test (real IndexedDB)
+        env:
+          PLAYWRIGHT_BROWSERS_PATH: ${{ github.workspace }}/.pw-browsers
+        run: |
+          python3 -m pytest labs/tests/test_wasm_persistence.py -v --override-ini="addopts="
+
   # ===========================================================================
   # Stage 4: Link integrity (Tier 2 — non-blocking baseline)
   # ===========================================================================