Add knowledgebases

Knowledgebases give bots RAG over documents, scoped like extensions: to
particular bots, to a workspace, or to every bot, with their own button
beside Tools in the composer. Documents are chunked and embedded by the
file-ingest worker with the install's embedding model, which is now an
install-wide setting rather than a per-bot one.

- Word search runs on an FTS5 index ranked by BM25, with a scored LIKE
  fallback for scripts written without spaces.
- Changing the embedding model re-indexes documents automatically.
- Ingest jobs wait without spending attempts while every embedding model
  rests, fail at once on errors retrying can't fix, and keep passages
  searchable by words when the model refuses.
- Settings > Knowledgebases shows each knowledgebase's and document's
  index state: spinner, warning, grey check (words only) or green check.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/utils/knowledgebase-index-state.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, test } from "bun:test";
+import knowledgebaseIndexState from "./knowledgebase-index-state";
+
+const base = { total: 3, indexing: 0, failed: 0, stale: 0, embedding_model: "model" };
+
+describe("knowledgebaseIndexState", () => {
+    test("is indexed when every document is read by the current model", () => {
+        expect(knowledgebaseIndexState(base)).toBe("indexed");
+    });
+
+    test("puts being read before a failure, and a failure before the model", () => {
+        expect(knowledgebaseIndexState({ ...base, indexing: 1, failed: 1 })).toBe("indexing");
+        expect(knowledgebaseIndexState({ ...base, failed: 1, embedding_model: null })).toBe("failed");
+    });
+
+    test("is words only without a model, stale with another one", () => {
+        expect(knowledgebaseIndexState({ ...base, stale: 3, embedding_model: null })).toBe("words");
+        expect(knowledgebaseIndexState({ ...base, stale: 1 })).toBe("stale");
+    });
+
+    test("is empty with no documents", () => {
+        expect(knowledgebaseIndexState({ ...base, total: 0, indexing: 1 })).toBe("empty");
+    });
+});