feat(evidence): add Qdrant BM25 vector in place

backend/test/qdrant-collection.test.ts

@@ -28,6 +28,90 @@ const compatible = (size = 1024, distance = "Cosine", schema = payloadSchema) =>
   payload_schema: schema,
 });
 
+test("Evidence maintenance adds an absent BM25 vector without changing the dense contract", async () => {
+  const info = compatible();
+  const requests: Array<{ url: string; init?: any }> = [];
+  const request = async (url: string, init?: any) => {
+    requests.push({ url, init });
+    if (init?.method === "PUT" && /\/vectors\/bm25$/.test(url)) {
+      expect(JSON.parse(String(init.body))).toEqual({ sparse: { modifier: "idf" } });
+      (info.config.params as any).sparse_vectors = { bm25: { modifier: "idf" } };
+      return { status: 200, ok: true, json: async () => ({}) } as any;
+    }
+    return { status: 200, ok: true, json: async () => ({ result: info }) } as any;
+  };
+
+  const result = await reconcileCollection({
+    baseUrl: "http://qdrant:6333", collection: "c", dimensions: 1024, distance: "cosine",
+    mode: "evidence_maintenance", request,
+  });
+
+  expect(result).toEqual({ ok: true, state: "upgraded" });
+  expect(info.config.params.vectors).toEqual({ size: 1024, distance: "Cosine" });
+  expect(requests.filter(({ init }) => init?.method === "PUT")).toHaveLength(1);
+  expect(requests[1]?.url).toBe("http://qdrant:6333/collections/c/vectors/bm25");
+});
+
+test("Evidence maintenance creates a missing collection with both required vector contracts", async () => {
+  let info: any;
+  let createdBody: any;
+  const request = async (url: string, init?: any) => {
+    if (init?.method === "PUT") {
+      createdBody = JSON.parse(String(init.body));
+      info = { config: { params: createdBody }, payload_schema: payloadSchema };
+      return { status: 200, ok: true, json: async () => ({}) } as any;
+    }
+    if (info === undefined) return { status: 404, ok: false, json: async () => ({}) } as any;
+    return { status: 200, ok: true, json: async () => ({ result: info }) } as any;
+  };
+
+  const result = await reconcileCollection({
+    baseUrl: "http://qdrant:6333", collection: "c", dimensions: 1024, distance: "cosine",
+    mode: "evidence_maintenance", request,
+  });
+
+  expect(result).toEqual({ ok: true, state: "ready" });
+  expect(createdBody).toEqual({
+    vectors: { size: 1024, distance: "Cosine" },
+    sparse_vectors: { bm25: { modifier: "idf" } },
+  });
+});
+
+test("Evidence maintenance refuses an incompatible BM25 definition without mutating", async () => {
+  const info = compatible();
+  (info.config.params as any).sparse_vectors = { bm25: { modifier: "none" } };
+  const requests: Array<{ url: string; init?: any }> = [];
+  const request = async (url: string, init?: any) => {
+    requests.push({ url, init });
+    return { status: 200, ok: true, json: async () => ({ result: info }) } as any;
+  };
+
+  const result = await reconcileCollection({
+    baseUrl: "http://qdrant:6333", collection: "c", dimensions: 1024, distance: "cosine",
+    mode: "evidence_maintenance", request,
+  });
+
+  expect(result).toEqual({ ok: false, code: "semantic_index_incompatible" });
+  expect(requests.filter(({ init }) => init?.method === "PUT")).toEqual([]);
+});
+
+test("ordinary session reconciliation does not add BM25", async () => {
+  const info = compatible();
+  const requests: Array<{ url: string; init?: any }> = [];
+  const request = async (url: string, init?: any) => {
+    requests.push({ url, init });
+    return { status: 200, ok: true, json: async () => ({ result: info }) } as any;
+  };
+
+  const result = await reconcileCollection({
+    baseUrl: "http://qdrant:6333", collection: "c", dimensions: 1024, distance: "cosine",
+    mode: "self_heal", request,
+  });
+
+  expect(result).toEqual({ ok: true, state: "ready" });
+  expect(requests.filter(({ url }) => /\/vectors\/bm25$/.test(url))).toEqual([]);
+});
+
 test("self-heal creates a missing compatible collection", async () => {
   const r = await reconcileCollection({
     baseUrl: "http://qdrant:6333", collection: "c", dimensions: 1024, distance: "cosine",