fix(client): degrade against a node still speaking MNP 1.0

The SPA is served by the hub, so deploying the hub puts this client in front of
every node — including the ones not updated yet. That window is the normal
state for as long as an operator takes, and for a node someone else runs it may
be indefinite. Three controls were broken across it, and the failure mode is
quiet: an unknown message type is logged by the node and never answered, so the
click produces a thirty-second wait ending in a timeout with nothing on screen
to say the node simply cannot do this.

Files' Upload button read `root.writable`, which a 1.0 node does not send — it
says `upload`, the same answer under the older name. The button disappeared on
every un-upgraded node. It reads both now, and still respects an explicit
`writable: false` rather than falling through to the legacy flag.

The per-app folder pickers spoke `app_directories`. Videos, Music and Photos
each had their own message before that and those still work, so the page
chooses by version: an operator on an older node keeps the ability they had.
`video_root` and `audio_root` hold one folder, so several are refused with a
reason rather than stored as the first and silently truncated.

Root management — writable, removable, eject, plug — has no older equivalent to
route to, so the table goes read-only with a line saying why and pointing at
the `meshbay-node root` commands. Chat's two settings are new with nothing
before them and are hidden the same way.

None of this was inferred from a payload's shape: `_checkNodeVersion` already
parsed the node's version and threw it away, and it is kept now. Coupling a
capability to whether some field happens to be present is how a flag flips
because an unrelated payload changed.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/packages/meshbay-hub/tests/test_app_settings_plugin.py b/packages/meshbay-hub/tests/test_app_settings_plugin.py
index 00a07b0..1837c28 100644
--- a/packages/meshbay-hub/tests/test_app_settings_plugin.py
+++ b/packages/meshbay-hub/tests/test_app_settings_plugin.py
@@ -226,9 +226,12 @@ def test_the_page_performs_exactly_one_app_specific_operation():
     # The page's own settings, which belong to no app: which apps are enabled
     # at all, and how hard the node works watching its disk.
     page_level = {"setAppsEnabled", "setScanSettings"}
-    assert calls - page_level == {"setAppDirectories"}, (
+    # Both are the same generic operation; the second is what a node too old
+    # for it understands, chosen by version rather than by app.
+    generic = {"setAppDirectories", "setAppDirectoriesLegacy"}
+    assert calls - page_level == generic, (
         f"the settings page performs app-specific operations: "
-        f"{sorted(calls - page_level - {'setAppDirectories'})}")
+        f"{sorted(calls - page_level - generic)}")
 
 
 # ── The apps read a list ────────────────────────────────────────────────────