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

tests/unit/test_ci_config.py

@@ -0,0 +1,39 @@
+"""Meta-gate checks for the CI workflow and pre-commit hook configuration."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+CI = ROOT / ".github" / "workflows" / "ci.yml"
+PRECOMMIT = ROOT / ".pre-commit-config.yaml"
+
+HEADLESS_COMMAND = 'pytest tests/unit tests/services -m "not slow"'
+
+
+def test_ci_declares_all_jobs() -> None:
+    """The workflow exposes the lint/type/test split as separate jobs."""
+    text = CI.read_text(encoding="utf-8")
+    for job in ("lint:", "type:", "test-headless:", "test-gui:", "test-integration:"):
+        assert f"\n  {job}\n" in text, f"missing CI job: {job}"
+
+
+def test_ci_runs_the_headless_command() -> None:
+    """The headless job runs the unit + services, non-slow command verbatim."""
+    assert HEADLESS_COMMAND in CI.read_text(encoding="utf-8")
+
+
+def test_precommit_declares_expected_hooks() -> None:
+    """The pre-commit config wires up the lint/format/type/hygiene hooks."""
+    text = PRECOMMIT.read_text(encoding="utf-8")
+    for hook in (
+        "id: ruff",
+        "id: ruff-format",
+        "id: mypy",
+        "id: trailing-whitespace",
+        "id: end-of-file-fixer",
+        "id: check-yaml",
+        "id: check-added-large-files",
+        "id: check-merge-conflict",
+    ):
+        assert hook in text, f"missing pre-commit hook: {hook}"