feat(hub): cap a directory zip at 512 MB

An arbitrary ceiling, not a technical one: the zip writer streams and holds
one chunk plus a record per file, so it would happily produce a hundred
gigabytes. Past half a gigabyte the honest answer is a subfolder at a time,
or the files individually.

Enforced in file-utils.js's downloadDirectory, which is the one
implementation behind every zip button — Files' single folder, Files'
multi-folder selection, and the Photos album button (docs/photos.md §3).

- Per directory, not per selection: Files zips a whole multi-directory
  selection in one click, so an oversized folder is refused and its siblings
  still download.
- Before _openDownloadTarget, so no save dialog opens for an archive that is
  never going to be written.
- The bound is strict, so a folder of exactly 512 MB still goes through.
- Counted in the 1024-based units formatSize already prints, so the number in
  the refusal is the number in the constant.

group.zip_too_large in all ten catalogues. test_zip_size_limit.py runs the
module under Node and pins the refusal, the inclusive bound, and that nothing
is asked or started when a folder is over.

The user guide's "a 40 GB folder costs 40 GB of disk" is no longer true and
now documents the cap instead.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V8EDjk6pkYZrCbo63m2x87

1 files changed, 2 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
index 6ae92cc..c61b8e5 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
@@ -592,6 +592,8 @@ export default {
   'group.zip_no_stream': 'Questo browser non sa scrivere un download direttamente su '
     + 'disco, quindi {name} ({size}) deve prima essere costruito in memoria. Con un '
     + 'archivio grande l’operazione può fallire. Continuare?',
+  'group.zip_too_large': '«{name}» occupa {size} e una cartella può essere scaricata in zip solo fino '
+    + 'a {limit}. Prendi una sottocartella alla volta, o i file singolarmente.',
   'group.rmdir': 'Elimina la cartella',
   'group.rmdir_confirm': 'Eliminare la cartella «{name}»? Deve essere vuota.',
   'group.rmdir_not_empty': 'Quella cartella non è vuota. Elimini prima ciò che '