feat: Engineering Knowledge Layer V1 — entities + relationships

Layer 2 of the AtoCore architecture. Adds typed engineering entities
with relationships on top of the flat memory/state/chunk substrate.

Schema:
- entities table: id, entity_type, name, project, description,
  properties (JSON), status, confidence, source_refs, timestamps
- relationships table: source_entity_id, target_entity_id,
  relationship_type, confidence, source_refs

15 entity types: project, system, subsystem, component, interface,
requirement, constraint, decision, material, parameter,
analysis_model, result, validation_claim, vendor, process

12 relationship types: contains, part_of, interfaces_with,
satisfies, constrained_by, affected_by_decision, analyzed_by,
validated_by, depends_on, uses_material, described_by, supersedes

Service layer: full CRUD + get_entity_with_context (returns an
entity with its relationships and all related entities in one call).

API endpoints:
- POST /entities — create entity
- GET /entities — list/filter by type, project, status, name
- GET /entities/{id} — entity + relationships + related entities
- POST /relationships — create relationship

Schema auto-initialized on app startup via init_engineering_schema().

7 tests covering entity CRUD, relationships, context traversal,
filtering, name search, and validation.

Test count: 290 -> 297.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_engineering.py

@@ -0,0 +1,118 @@
+"""Tests for the Engineering Knowledge Layer."""
+
+from atocore.engineering.service import (
+    ENTITY_TYPES,
+    RELATIONSHIP_TYPES,
+    create_entity,
+    create_relationship,
+    get_entities,
+    get_entity,
+    get_entity_with_context,
+    get_relationships,
+    init_engineering_schema,
+)
+from atocore.models.database import init_db
+
+import pytest
+
+
+def test_create_and_get_entity(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    e = create_entity(
+        entity_type="component",
+        name="Pivot Pin",
+        project="p04-gigabit",
+        description="Lateral support pivot pin for M1 assembly",
+        properties={"material": "GF-PTFE", "diameter_mm": 12},
+    )
+    assert e.entity_type == "component"
+    assert e.name == "Pivot Pin"
+    assert e.properties["material"] == "GF-PTFE"
+
+    fetched = get_entity(e.id)
+    assert fetched is not None
+    assert fetched.name == "Pivot Pin"
+
+
+def test_create_relationship(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    subsystem = create_entity("subsystem", "Lateral Support", project="p04-gigabit")
+    component = create_entity("component", "Pivot Pin", project="p04-gigabit")
+
+    rel = create_relationship(
+        source_entity_id=subsystem.id,
+        target_entity_id=component.id,
+        relationship_type="contains",
+    )
+    assert rel.relationship_type == "contains"
+
+    rels = get_relationships(subsystem.id, direction="outgoing")
+    assert len(rels) == 1
+    assert rels[0].target_entity_id == component.id
+
+
+def test_entity_with_context(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    subsystem = create_entity("subsystem", "Lateral Support", project="p04-gigabit")
+    pin = create_entity("component", "Pivot Pin", project="p04-gigabit")
+    pad = create_entity("component", "PTFE Pad", project="p04-gigabit")
+    material = create_entity("material", "GF-PTFE", project="p04-gigabit",
+                             description="Glass-filled PTFE for thermal stability")
+
+    create_relationship(subsystem.id, pin.id, "contains")
+    create_relationship(subsystem.id, pad.id, "contains")
+    create_relationship(pad.id, material.id, "uses_material")
+
+    ctx = get_entity_with_context(subsystem.id)
+    assert ctx is not None
+    assert len(ctx["relationships"]) == 2
+    assert pin.id in ctx["related_entities"]
+    assert pad.id in ctx["related_entities"]
+
+
+def test_filter_entities_by_type_and_project(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    create_entity("component", "Pin A", project="p04-gigabit")
+    create_entity("component", "Pin B", project="p04-gigabit")
+    create_entity("material", "Steel", project="p04-gigabit")
+    create_entity("component", "Actuator", project="p06-polisher")
+
+    components = get_entities(entity_type="component", project="p04-gigabit")
+    assert len(components) == 2
+
+    all_p04 = get_entities(project="p04-gigabit")
+    assert len(all_p04) == 3
+
+    polisher = get_entities(project="p06-polisher")
+    assert len(polisher) == 1
+
+
+def test_invalid_entity_type_raises(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    with pytest.raises(ValueError, match="Invalid entity type"):
+        create_entity("spaceship", "Enterprise")
+
+
+def test_invalid_relationship_type_raises(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    a = create_entity("component", "A")
+    b = create_entity("component", "B")
+    with pytest.raises(ValueError, match="Invalid relationship type"):
+        create_relationship(a.id, b.id, "loves")
+
+
+def test_entity_name_search(tmp_data_dir):
+    init_db()
+    init_engineering_schema()
+    create_entity("component", "Vertical Support Pad")
+    create_entity("component", "Lateral Support Bracket")
+    create_entity("component", "Reference Frame")
+
+    results = get_entities(name_contains="Support")
+    assert len(results) == 2