Stop storing raw file bytes in media.text_content

`text_content` is an extracted-text cache, but nothing stopped it from
holding a dump of bytes:

- `fileToText` ended its switch with `default: return buffer.toString("utf-8")`
  and defaulted a missing extension to "txt", so any binary was decoded.
- Both extraction callers gated on `media_type == "document"`, and
  `attachmentFileKind` classes everything non-image/audio/video as a
  document: an SVG, a zip, a spreadsheet, a .bin.
- Nothing capped the length, so a 20 MB attachment could leave 20 MB of
  text in the database.
- `storeChatAttachments` copied the text onto a second `media` row, and
  `SELECT m.*` pulled the column into page props and API responses.

On a real install an SVG held 6852 characters of markup and a
`.designcraft` file held 142 KB of raw bytes.

Changes:

- `file-to-text.ts` lists the text extensions explicitly and returns
  undefined for anything else; no extension is no text.
- `can-extract-text.ts` is the one allowlist (reusing
  `BotTextFileExtensions`), used by both upload routes and by
  `uploadAndRecordMedia`; `extension-of.ts` is shared with the storage
  catalog instead of duplicated.
- `BotAttachmentTextStoreMaxChars` (200k) caps the column via
  `cap-text-content.ts`.
- `store-chat-attachments.ts` no longer copies the text; ingestion
  re-reads the bytes once.
- `media-columns.ts` selects every media column but `text_content`, which
  now has to be asked for (`grab-messages-media`'s reply path and
  ingestion do); the media CRUD routes sanitize rows they write.
- `ingest-bot-file.ts` decides on size alone, since a cached slice made
  an oversized file look already read.
- `bun run media:prune-text` cleans rows that were already stored
  (rerunnable, with a VACUUM hint).

Verified on the dev database: both bad rows cleared (146 KB), rerun
reports nothing to do.

src/functions/backend/db/bot-files/store-chat-attachments.ts

@@ -1,4 +1,3 @@
-import BunSQLite from "@moduletrace/bun-sqlite";
 import type { BUN_SQLITE_COBBLE_MEDIA } from "@/db/types/db";
 import { BotUploadFolder } from "@/src/dict/bot-file-dict";
 import enqueueFileIngest from "@/src/file-ingest/enqueue-file-ingest";
@@ -44,6 +43,13 @@ export default async function storeChatAttachments({
              */
             const name = safeName({ name: file.title || `file-${file.id}` });
 
+            /**
+             * The text stays on the message's own `bot-attachment` row,
+             * where a reply reads it. Copying it onto the file's row kept
+             * the same text twice and left the copy behind when the
+             * upload was pruned; ingestion re-reads the bytes once
+             * through `extractBotFileText` instead.
+             */
             const saved = await recordBotFile({
                 bot_id,
                 scope: workspace_id ? "workspace" : "bot",
@@ -57,17 +63,6 @@ export default async function storeChatAttachments({
                 user_id,
             });
 
-            /**
-             * The same text the upload already extracted, so a PDF isn't
-             * unpacked a second time.
-             */
-            if (file.text_content && saved.media_id) {
-                await BunSQLite.sql({
-                    sql: `UPDATE media SET text_content = ? WHERE id = ?`,
-                    values: [file.text_content, saved.media_id],
-                }).catch(() => {});
-            }
-
             await enqueueFileIngest({ file_id: saved.id! });
         } catch (error) {
             await logError({