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/extension-option-value.ts

@@ -1,7 +1,7 @@
 import type { BotExtension } from "@/src/types";
 
 /**
- * An MCP server, tool or skill as one select value (`mcp:3`), and back.
+ * An MCP server, tool, skill or knowledgebase as one select value (`mcp:3`), and back.
  */
 export function extensionOptionValue({ kind, id }: { kind: BotExtension["kind"]; id: number }) {
     return `${kind}:${id}`;
@@ -10,7 +10,7 @@ export function extensionOptionValue({ kind, id }: { kind: BotExtension["kind"];
 export function parseExtensionOptionValue({ value }: { value: string }) {
     const [kind, id] = value.split(":");
 
-    if ((kind != "mcp" && kind != "tool" && kind != "skill") || !Number(id)) return null;
+    if ((kind != "mcp" && kind != "tool" && kind != "skill" && kind != "knowledgebase") || !Number(id)) return null;
 
     return { kind: kind as BotExtension["kind"], id: Number(id) };
 }