Names quak builds from server data fit in 255 bytes (closes #205)

The default names of `quak get`, `quak get-thumb`, `downloadFile` and
`downloadThumbnail`, and the album folders of `backup-metadata`, could be
over 255 bytes, which a file system refuses. `shortenKeepingExtension` in
`src/filename.ts` cuts a name short, keeping its extension when it fits,
and can put text right before the extension; the backup's `withID` now
calls it instead of doing the same itself. The `get` defaults use it with
`thumb_` counted. A `backup-metadata` folder keeps its `<id>-` and has the
name after it cut short. `safeExtension` gives `.bin` for an extension of
more than 16 letters and digits, so a save path's name always fits.

Model: opus-5-5

src/download/index.ts

@@ -16,7 +16,13 @@ import {
     streamTagFinal,
 } from "../crypto/index.js";
 import { TruncatedStreamError } from "../errors.js";
-import { safeExtension, sanitizeFileName, withExtension } from "../filename.js";
+import {
+    MAX_NAME_BYTES,
+    safeExtension,
+    sanitizeFileName,
+    shortenKeepingExtension,
+    withExtension,
+} from "../filename.js";
 import { withRetry } from "../retry.js";
 import type { ApiClient } from "../api/client.js";
 import type { EnteFile } from "../model/types.js";
@@ -583,9 +589,14 @@ export const downloadFile = async (
     onProgress?: ProgressCallback,
 ): Promise<DownloadResult> => {
     // `outPath` is the caller's and is used as is; the title is the server's
-    // and is sanitized so it can only name a file in the current directory.
+    // and is sanitized so it can only name a file in the current directory,
+    // and cut short to fit in a file name, keeping its extension.
     const resolvedPath =
-        outPath ?? sanitizeFileName(file.metadata.title, `file-${file.id}`);
+        outPath ??
+        shortenKeepingExtension(
+            sanitizeFileName(file.metadata.title, `file-${file.id}`),
+            MAX_NAME_BYTES,
+        );
     const header = fromBase64(file.file.decryptionHeader);
     return fetchAndDecrypt(
         api,
@@ -604,9 +615,14 @@ export const downloadThumbnail = async (
     outPath?: string,
     onProgress?: ProgressCallback,
 ): Promise<DownloadResult> => {
+    // As in `downloadFile`, with `thumb_` before the title.
     const resolvedPath =
         outPath ??
-        `thumb_${sanitizeFileName(file.metadata.title, `file-${file.id}`)}`;
+        "thumb_" +
+            shortenKeepingExtension(
+                sanitizeFileName(file.metadata.title, `file-${file.id}`),
+                MAX_NAME_BYTES - "thumb_".length,
+            );
     const header = fromBase64(file.thumbnail.decryptionHeader);
     return fetchAndDecrypt(
         api,