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/pages/admin/settings/knowledgebases/(functions)/knowledgebase-summary.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, test } from "bun:test";
+import knowledgebaseSummary from "./knowledgebase-summary";
+
+const empty = { document_count: 0, pending_count: 0, error_count: 0, stale_count: 0, size: 0 };
+
+describe("knowledgebaseSummary", () => {
+    test("an empty knowledgebase says so", () => {
+        expect(knowledgebaseSummary({ knowledgebase: empty })).toBe("No documents yet");
+    });
+
+    test("counts documents and names only the problems there are", () => {
+        expect(knowledgebaseSummary({ knowledgebase: { ...empty, document_count: 1, size: 2048 } })).toBe(
+            "1 document · 2.0 KB",
+        );
+        expect(
+            knowledgebaseSummary({
+                knowledgebase: { document_count: 3, pending_count: 1, error_count: 1, stale_count: 2, size: 2048 },
+            }),
+        ).toBe("3 documents · 2.0 KB · 1 being read · 1 couldn't be read · 2 need re-indexing");
+    });
+});