docs(IMP-52): reconcile Phase Z family count drift -- F-2 option (c)

Audit follow-up F-2 (INTEGRATION-AUDIT-01 §10.2). Phase Z families surface
showed 11 tracked / 11 contracted / 13 on disk. The 2 untracked WIP files
(app_sw_package_vs_solution.html, pre_construction_model_info_stacked.html)
are now declared in _WIP_FILES.md as uncontracted and out-of-scope for the
runtime matcher; promote/remove is gated on #42. The 11/11 tracked +
contracted baseline is unchanged. A new pytest enforces tracked families ↔
frame_contracts.yaml set-equality modulo the WIP allowlist parsed from
_WIP_FILES.md, so future drift fails fast in CI before #42 expands to 32
frames.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_family_contract_baseline.py

@@ -0,0 +1,80 @@
+"""Phase Z family-template ↔ frame_contracts.yaml baseline invariant.
+
+#52 F-2 option (c) lock (2026-05-19) — locks active contracted family count
+at 11/11 with a WIP allowlist for the 2 untracked WIP family templates
+documented in `templates/phase_z2/families/_WIP_FILES.md`. Any drift after
+this point (new family file on disk without a contract entry, or a contract
+entry pointing to a missing file) fails fast in CI.
+
+References:
+  - docs/architecture/INTEGRATION-AUDIT-01-REPORT.md §10.2 F-2
+  - docs/architecture/IMP-18-SVG-GAP-REPORT.md L28/L30/L51
+  - templates/phase_z2/families/_WIP_FILES.md (WIP allowlist source)
+  - Gitea #52 (this reconciliation), #42 (promote/remove gate)
+
+Pattern mirrors `tests/test_catalog_invariant.py` — fail fast with explicit
+diff message if family ↔ contract surfaces drift.
+"""
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+import yaml
+
+PROJECT_ROOT = Path(__file__).parent.parent
+FAMILIES_DIR = PROJECT_ROOT / "templates" / "phase_z2" / "families"
+CATALOG_PATH = PROJECT_ROOT / "templates" / "phase_z2" / "catalog" / "frame_contracts.yaml"
+WIP_DOC_PATH = FAMILIES_DIR / "_WIP_FILES.md"
+
+
+def _load_contract_keys() -> set[str]:
+    with CATALOG_PATH.open(encoding="utf-8") as f:
+        catalog = yaml.safe_load(f)
+    return {k for k, v in catalog.items() if isinstance(v, dict)}
+
+
+def _load_disk_family_stems() -> set[str]:
+    return {p.stem for p in FAMILIES_DIR.glob("*.html")}
+
+
+def _load_wip_allowlist() -> set[str]:
+    text = WIP_DOC_PATH.read_text(encoding="utf-8")
+    return {m.group(1) for m in re.finditer(r"`([A-Za-z0-9_\-]+)\.html`", text)}
+
+
+def test_contracts_set_equals_disk_families_minus_wip():
+    """`frame_contracts.yaml` keys ↔ disk family stems minus WIP allowlist."""
+    contracts = _load_contract_keys()
+    disk = _load_disk_family_stems()
+    wip = _load_wip_allowlist()
+    expected = disk - wip
+    missing = expected - contracts
+    extra = contracts - expected
+    assert not missing, (
+        f"Family files on disk without frame_contracts.yaml entry "
+        f"(and not in _WIP_FILES.md): {sorted(missing)}. "
+        "Add a contract entry, or list the file in "
+        "templates/phase_z2/families/_WIP_FILES.md as WIP."
+    )
+    assert not extra, (
+        f"frame_contracts.yaml has entries with no matching family file: "
+        f"{sorted(extra)}."
+    )
+
+
+def test_wip_allowlist_is_disk_only_and_uncontracted():
+    """WIP allowlist names must exist on disk AND have no contract entry."""
+    contracts = _load_contract_keys()
+    disk = _load_disk_family_stems()
+    wip = _load_wip_allowlist()
+    missing_on_disk = wip - disk
+    leaked_into_contracts = wip & contracts
+    assert not missing_on_disk, (
+        f"_WIP_FILES.md names files not on disk: {sorted(missing_on_disk)}."
+    )
+    assert not leaked_into_contracts, (
+        f"_WIP_FILES.md names files that already have a contract entry: "
+        f"{sorted(leaked_into_contracts)}. Promote via #42 instead — "
+        "WIP allowlist must be disk-only / uncontracted."
+    )