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/data/app-data.ts

@@ -638,6 +638,17 @@ export const AppData = {
     RagTopChunks: 8,
     RagOverFetch: 4,
     RagMaxK: 60,
+    /**
+     * Knowledgebases: the most one document holds (an upload, or text
+     * written in), how much of a pasted text a form takes, how many
+     * passages a reply is handed before the bot asks for any (retrieved
+     * for the newest user message), and how much of a document
+     * `read_knowledgebase_document` hands back at once.
+     */
+    KnowledgebaseDocumentMaxBytes: 20 * 1024 * 1024,
+    KnowledgebaseTextMaxChars: 200_000,
+    KnowledgebaseAutoPassages: 4,
+    KnowledgebaseReadMaxChars: 12_000,
     FileIngestPollMs: 5000,
     FileIngestConcurrency: 2,
     FileIngestWorker: "ingest",