feat(documents): expose content-index provenance on the document DTO

Surface the content-search index's source (vision vs local extraction) on
the list + detail DTO so the vault UI can tell an AI-read document from a
locally-indexed one. Threads the source through both read paths and the
serialisers, regenerates the OpenAPI contract, and adds a narrowing helper
for the free-String column.

src/components/documents/__tests__/document-card.test.tsx

@@ -32,6 +32,7 @@ function doc(overrides: Partial<InboundDocumentDto> = {}): InboundDocumentDto {
     conditionLinks: [{ episodeId: "ep-knee", name: "Knie" }],
     servingClass: "inline",
     hasContentIndex: false,
+    contentIndexSource: null,
     createdAt: "2025-10-05T08:00:00.000Z",
     updatedAt: "2025-10-05T08:00:00.000Z",
     ...overrides,

src/components/documents/__tests__/episode-documents-card.test.tsx

@@ -52,6 +52,7 @@ function doc(id: string, title: string): InboundDocumentDto {
     conditionLinks: [{ episodeId: "ep1", name: "Knee" }],
     servingClass: "inline",
     hasContentIndex: false,
+    contentIndexSource: null,
     createdAt: "2025-10-05T08:00:00.000Z",
     updatedAt: "2025-10-05T08:00:00.000Z",
   };

src/components/documents/__tests__/vault-utils.test.ts

@@ -33,6 +33,7 @@ function doc(overrides: Partial<InboundDocumentDto> = {}): InboundDocumentDto {
     conditionLinks: [],
     servingClass: "inline",
     hasContentIndex: false,
+    contentIndexSource: null,
     createdAt: "2026-03-11T08:00:00.000Z",
     updatedAt: "2026-03-11T08:00:00.000Z",
     ...overrides,