add SimConfig, free CMR clock assignment, top-4 cluster collection

Replace 11+ bare args on run_sweep_loop with a single &SimConfig
backed by typed enums and validator-based cross-field checks.

New features:
- Free CMR overlap update: independently flip each replica (SW) or
  pick uniformly from {flip_a, flip_b, flip_both} (Wolff) instead
  of swapping σ^a ↔ σ^b. Validated to require houdayer_mode=cmr.
- Top-4 cluster sizes: opt-in collection of average relative sizes
  of the 4 largest overlap clusters per temperature.

Split spin glass Binder tests into tests/spin_glass_crossings.py
so CI can run ferromagnet and spin glass suites in parallel.

Signed-off-by: PeaBrane <peabrane@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: PeaBrane

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
       - run: cargo clippy -- -D warnings
       - run: cargo test
 
-  test-python:
+  test-ferromagnets:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -53,5 +53,30 @@ jobs:
           uv pip install maturin numpy matplotlib
           maturin develop --release
 
-      - name: Binder crossings
+      - name: Binder crossings (ferromagnets)
         run: source .venv/bin/activate && cd tests && python binder_crossings.py
+
+  test-spin-glass:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+
+      - name: Build and install
+        run: |
+          uv venv .venv
+          source .venv/bin/activate
+          uv pip install maturin numpy matplotlib
+          maturin develop --release
+
+      - name: Binder crossings (spin glass)
+        run: source .venv/bin/activate && cd tests && python spin_glass_crossings.py