Files: never an empty pane -- Loading…, a slow answer and a refusal said in the tree

Files › Server drew nothing while GET /files was on its way: no word that it was being read, and a
refusal or a broken answer only after Rust's 60 s read timeout. To the administrator it looked as
if the server had no files, until the listing arrived. Every folder of both trees now says
Loading… while it is read, says after 8 s that the server has not answered (with Try again, the
late answer still drawn), and says a refusal, an answer that is not a listing, or a failure to
draw it in its place with Try again. An answer that comes after Read again, or after the folder
was closed, is dropped instead of appended beside the new one.

Tests (tests/ui N8): the administrator's / as the server's test client answers it (folders, a
mount, files at the root), held to show Loading…; the 8 s note under a fake clock; a 403 and Try
again; three answers that are not a listing; Read again while an answer is pending; 390 px. The
mock can hold an answer (`hold`, `__mock.release`) and change one (`__mock.answer`).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -4,6 +4,19 @@ All notable changes to LLeMbas Desktop. The format follows
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and the project uses
 [Semantic Versioning](https://semver.org/).
 
+## [Unreleased]
+
+### Fixed
+
+- **Files › Server showed an empty pane while it waited.** Nothing was drawn until the server's
+  listing came back -- no word that it was being read -- and a refusal or a broken answer was said
+  only once Rust's read timeout (60 s) had passed; to the person it looked as if there were no
+  files at all. Every folder in both trees now says Loading… while it is read; after 8 s it says
+  the server has not answered yet and offers Try again (the late answer is still drawn); a
+  refusal, an answer that is not a listing, or anything that breaks drawing it is said in its
+  place with Try again. Read again while an answer was on its way no longer draws the listing
+  twice.
+
 ## [1.0.0-beta.7] — 2026-11-10
 
 LLeMbas CLI 2.0.0-beta.7 inside, the look and words of LLeMbas 2.0.0-beta.9.