feat(client): bring back New folder, icon-only — and close the hole it opened

The control was hidden and its `canCreateDir` left computed and unused. It is
back in the Files toolbar as an icon: the toolbar already carries one labelled
primary action, and a second beside it competes for the width the breadcrumb
trail needs. The name is in `title` *and* `aria-label` — a title is invisible
to a screen reader on a button with no text, so an icon-only control without
both is simply unnamed for anyone not reading with their eyes.

Its gate changes. It required `isNodeAdmin`, which contradicted the node's own
rule — "making a directory is not a privileged act; a member who can add a file
can organise where it goes" — and hid the control from everyone who could have
used it. It now follows the Upload button: a writable root, and not at the top
of a group, where the level is the set of roots rather than a directory on
anyone's disk.

Restoring it surfaced a real gap. `_do_dir_create` never learned about RO/RW:
`_do_file_upload` gained the `writable` check with the model and this one did
not, so a member refused a file in a published library could still leave empty
directories all through it, and could write to a drive mid-eject. Read-only has
to mean read-only for every way of writing, not just for files.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011pvMdvLBG92jyhvD5pD6us

1 files changed, 4 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/style.css b/packages/meshbay-hub/src/meshbay_hub/static/style.css
index 0441e14..4647209 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/style.css
+++ b/packages/meshbay-hub/src/meshbay_hub/static/style.css
@@ -833,6 +833,10 @@ button:disabled { opacity: 0.5; cursor: not-allowed; }
 .tb-btn:disabled { opacity: 0.45; cursor: not-allowed; }
 .tb-btn:disabled:hover { border-color: var(--border); color: var(--text); }
 .tb-btn .icon { width: 15px; height: 15px; }
+/* Square, for a toolbar button whose name is in its tooltip rather than
+   beside it. The horizontal padding goes; the height does not, so it lines up
+   with the labelled buttons next to it. */
+.tb-btn-icon { padding: 0; width: 32px; justify-content: center; gap: 0; }
 .tb-btn.primary {
   background: var(--accent);
   border-color: var(--accent);