feat(placements): v0.11 P5 learner placement visibility (REQ-11-005) [3/10] — wave 5-1: get_placement_by_application active-placement read (G-316 shape)

apps/ai-service/ai_service/placements/store.py

@@ -271,6 +271,15 @@ class PlacementStore(Protocol):
     def get_placement(self, placement_id: str) -> PlacementRow | None:
         ...
 
+    def get_placement_by_application(
+        self, application_id: str
+    ) -> PlacementRow | None:
+        """v0.11 P5 (REQ-11-005): the learner status read's placement
+        arm — the ACTIVE placement on this application (the G-316
+        partial-unique shape: at most one; revoked-only history →
+        None, the honest null — the events carry the correction)."""
+        ...
+
     def list_placements(self, status: str | None = None) -> list[PlacementRow]:
         ...
 
@@ -533,6 +542,25 @@ class SQLitePlacementStore:
             row._normalize()
             return row
 
+    def get_placement_by_application(
+        self, application_id: str
+    ) -> PlacementRow | None:
+        """v0.11 P5 (REQ-11-005): the ACTIVE placement on this
+        application — the G-316 partial unique index makes
+        at-most-one structural; revoked-only history → None (the
+        honest null — never a fabricated placement, A-304)."""
+        with Session(self._engine) as session:
+            row = session.exec(
+                select(PlacementRow).where(
+                    PlacementRow.application_id == application_id,
+                    PlacementRow.status == "active",
+                )
+            ).one_or_none()
+            if row is None:
+                return None
+            row._normalize()
+            return row
+
     def list_placements(self, status: str | None = None) -> list[PlacementRow]:
         """created_at then id (the list_postings ordering discipline,
         R-73 — deterministic export ordering)."""