Add gated Placement F2 pack skeleton for satellite xy.

Propose positions only from PCB footprints plus numeric decoupling max_distance_mm; otherwise skip with an explicit reason.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_placement_pack.py

@@ -0,0 +1,109 @@
+"""Layout F2 placement_pack — gated; no invented millimetres."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from backend.pinscopex.functional_groups import (
+    PlacementIcGroup,
+    PlacementSatellite,
+    FunctionalGroupsReport,
+    build_functional_groups,
+)
+from backend.pinscopex.models import (
+    DesignGraph,
+    LayoutFootprint,
+    LayoutGraph,
+    LayoutPad,
+)
+from backend.pinscopex.placement_pack import build_placement_pack
+
+SIMPLE = Path(__file__).resolve().parents[1] / "simple_project"
+
+
+def _graph() -> DesignGraph:
+    return DesignGraph.model_validate_json(
+        (SIMPLE / "design_graph.json").read_text(encoding="utf-8"),
+    )
+
+
+def test_simple_project_without_pcb_skips_pack():
+    plan = build_functional_groups(_graph())
+    pack = build_placement_pack(plan, None)
+    assert pack.status == "skipped"
+    assert pack.skip_reason == "no_pcb_footprints"
+    assert pack.placements == []
+
+
+def test_layout_without_numeric_rules_skips():
+    plan = FunctionalGroupsReport(
+        groups=[
+            PlacementIcGroup(
+                ref="U1",
+                layout_rules=[{"kind": "decoupling_proximity", "pin": "5"}],
+                satellites=[
+                    PlacementSatellite(
+                        ref="C4",
+                        component_type="capacitor",
+                        role_hint="decoupling",
+                        nets=["+3V3"],
+                    ),
+                ],
+            ),
+        ],
+    )
+    layout = LayoutGraph(
+        footprints={
+            "U1": LayoutFootprint(
+                reference="U1", x=0, y=0, layer="F.Cu",
+                pads=[LayoutPad(number="5", x=0.0, y=0.0, net="+3V3")],
+            ),
+        },
+    )
+    pack = build_placement_pack(plan, layout)
+    assert pack.status == "skipped"
+    assert pack.skip_reason == "no_numeric_layout_rules"
+
+
+def test_numeric_rule_proposes_satellite_within_limit():
+    limit = 2.0
+    plan = FunctionalGroupsReport(
+        groups=[
+            PlacementIcGroup(
+                ref="U1",
+                layout_rules=[{
+                    "kind": "decoupling_proximity",
+                    "pin": "5",
+                    "max_distance_mm": limit,
+                }],
+                satellites=[
+                    PlacementSatellite(
+                        ref="C4",
+                        component_type="capacitor",
+                        role_hint="decoupling",
+                        nets=["+3V3"],
+                    ),
+                ],
+            ),
+        ],
+    )
+    layout = LayoutGraph(
+        footprints={
+            "U1": LayoutFootprint(
+                reference="U1", x=0, y=0, layer="F.Cu",
+                pads=[LayoutPad(number="5", x=10.0, y=20.0, net="+3V3")],
+            ),
+        },
+    )
+    pack = build_placement_pack(plan, layout)
+    assert pack.status == "packed"
+    assert pack.skip_reason is None
+    assert len(pack.placements) == 1
+    p = pack.placements[0]
+    assert p.ref == "C4"
+    assert p.anchor_ref == "U1"
+    assert p.max_distance_mm == limit
+    assert p.layer == "F.Cu"
+    dist = ((p.proposed_x - 10.0) ** 2 + (p.proposed_y - 20.0) ** 2) ** 0.5
+    assert dist <= limit + 1e-6
+    assert dist > 0