feat: named case-result load combinations with full GUI support

Snapshots the current development tree, headlined by proper load
combinations (user request): a reusable LoadCombination entity of
weighted completed static-case results (e.g. 1.2xDead + 1.6xLive).

- core: LoadCombination/LoadCombinationItem entities, Project
  integration (lookup, unique ids, reference validation)
- services: combinations.py (linear superposition + envelope),
  exported via services __init__
- commands: undoable Add/Delete/Update for combinations
- GUI: Load Combinations manager dialog, Run-dialog evaluation,
  envelope display in Results panel, Combinations tab in Table dock
- tests: unit coverage (validation, math, error paths) + integration
  superposition check vs a single factored run

.github/workflows/ci.yml

@@ -0,0 +1,86 @@
+name: CI
+
+on:
+  push:
+    branches: [main, develop]
+  pull_request:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - run: pip install ruff
+      - run: ruff check src tests
+      - run: ruff format --check src tests
+
+  type:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - run: pip install -e ".[gui,dev]"
+      - run: mypy src/otko/core src/otko/services src/otko/viewmodels
+
+  test-headless:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ["3.10", "3.11", "3.12"]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - run: pip install -e ".[dev]"
+      - run: pytest tests/unit tests/services -m "not slow"
+
+  test-gui:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ["3.10", "3.11", "3.12"]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install Linux Qt deps
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libegl1 libxkbcommon-x11-0 libxcb-icccm4 \
+            libxcb-image0 libxcb-keysyms1 libxcb-randr0 libxcb-render-util0 \
+            libxcb-shape0 libxcb-sync1 libxcb-xfixes0 libxcb-xinerama0 \
+            libxcb-cursor0 libdbus-1-3 libgl1 libxkbcommon0 xvfb
+      - run: pip install -e ".[gui,dev]"
+      - name: Run GUI tests (Linux, headless)
+        if: runner.os == 'Linux'
+        run: xvfb-run -a pytest tests/gui
+      - name: Run GUI tests (Win/Mac)
+        if: runner.os != 'Linux'
+        run: pytest tests/gui
+
+  test-integration:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ["3.10", "3.11", "3.12"]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - run: pip install -e ".[gui,dev]"
+      - run: pytest tests/integration -m slow

.github/workflows/ci.yml.disabled

@@ -0,0 +1,48 @@
+name: CI
+
+on:
+  push:
+    branches: [main, develop]
+  pull_request:
+    branches: [main, develop]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      - run: pip install ruff mypy
+      - run: ruff check src tests
+      - run: ruff format --check src tests
+
+  test:
+    needs: lint
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ["3.10", "3.11", "3.12"]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install Linux Qt deps
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libegl1 libxkbcommon-x11-0 libxcb-icccm4 \
+            libxcb-image0 libxcb-keysyms1 libxcb-randr0 libxcb-render-util0 \
+            libxcb-shape0 libxcb-sync1 libxcb-xfixes0 libxcb-xinerama0 \
+            libxcb-cursor0 libdbus-1-3 libgl1 libxkbcommon0 xvfb
+      - run: pip install -e ".[dev]"
+      - name: Run tests (Linux, headless)
+        if: runner.os == 'Linux'
+        run: xvfb-run -a pytest --cov --cov-report=xml -m "not slow"
+      - name: Run tests (Win/Mac)
+        if: runner.os != 'Linux'
+        run: pytest --cov --cov-report=xml -m "not slow"