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/functions/backend/db/harness/save-workspace-harness-setting.ts

@@ -1,5 +1,5 @@
 import BunSQLite from "@moduletrace/bun-sqlite";
-import type { HarnessKind } from "@/src/dict/harness-dict";
+import { Harnesses, isInstallWideHarness, type HarnessKind } from "@/src/dict/harness-dict";
 import AppError from "@/src/utils/app-error";
 import assertHarnessModel from "./assert-harness-model";
 import assertHarnessProvider from "./assert-harness-provider";
@@ -48,6 +48,12 @@ export default async function saveWorkspaceHarnessSetting({
         return;
     }
 
+    if (isInstallWideHarness({ harness })) {
+        const title = Harnesses.find((h) => h.value == harness)?.title || harness;
+
+        throw new AppError(`${title} is set for the whole install, in Settings, under Models.`);
+    }
+
     if (harness == "text" && !enabled) {
         throw new AppError(`The text model can't be turned off.`);
     }