feat(client): Phase 2 — per-app settings panes, folder tree, multi-directory

Each app's settings were inlined in `group-settings.js` — TMDB, MusicBrainz,
and one folder picker per app, each with its own draft state and save handler
saying the same thing about a different key. They are one file per app now,
reached through the `apps.js` registry, and the page that renders them names no
application at all: adding one is a registry entry and a settings file.

The line between the two is what makes that true. What every app has — folders
— the page does generically, through one `saveDirectories` bound to the app.
What one app alone has, its pane does itself with the transport it is handed.
An app that only needs directories touches neither `group-settings.js` nor
`group-page.js`, which is `test_app_settings_plugin.py`'s subject.

`settings-ui.js` exists because a pane importing the page that renders it is a
cycle, and ES modules answer that with a temporal-dead-zone ReferenceError at
first render — a component that silently does not appear, the fault already
recorded in CLAUDE.md about hook ordering.

The flat depth-indented `<select>` of every folder in the library becomes a
modal tree. It asks the node for nothing: the tree is derived from paths the
client already holds, so it shows exactly what the group's index contains and
adds no folder-browsing protocol. For Chat's attachment folder — the one
directory that is written to rather than read — read-only roots are greyed
out, so the node's refusal arrives before the operator picks rather than when
somebody sends a file.

Videos and Music take a list of folders. A library on two drives could not be
described before; the only recourse was pointing the app at a parent containing
both, which pulls in everything else under it. The scalar shapes survive on the
wire alone, for a node speaking MNP 1.0, and the client reads them as a
one-element list.

Two things the tests caught that I would not have:

`test_asset_versioning` — six new modules were missing from `_ASSETS`. Reached
through the registry rather than imported by name, they are exactly the files
nothing else would notice changing, and a stale one is served from cache with
no version bump.

And `node --check foo.js` does **not** reliably report a module syntax error:
it accepted `${/* ... */''}` — htm template syntax pasted into a plain object
literal — and reported success. A `.mjs` copy forces the module parser and
reports it. The suite had no syntax check at all, which is how that reached a
file; `test_spa_syntax.py` does it for every module now, and pins that the
loose path is not what it uses.

Suite: 12 failures, all pre-existing.

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

1 files changed, 27 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
index f62d6fd..e0886a2 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
@@ -799,6 +799,33 @@ export default {
   'settings_node.photo_roots_save': '保存',
   'settings_node.shared_directories_title': '共享目录',
   'settings_node.shared_directories_hint': '与此群组共享的文件夹。切换读写以允许上传，标记为可移除用于外置驱动器。',
+  'folder_tree.title_single': '选择文件夹',
+  'folder_tree.title_multi': '选择文件夹',
+  'folder_tree.choose': '选择…',
+  'folder_tree.confirm': '使用',
+  'folder_tree.expand': '展开',
+  'folder_tree.collapse': '折叠',
+  'folder_tree.nothing_selected': '未选择',
+  'folder_tree.empty': '该群组还没有共享目录。',
+  'folder_tree.writable_only': '此处只能选择可读写的目录 — 文件会写入其中。',
+  'folder_tree.no_writable_root': '该群组没有可写目录。请先在「共享目录」中将某个目录设为读写。',
+  'folder_tree.read_only_blocked': '只读 — 无法写入',
+  'settings_app.save': '保存',
+  'settings_app.saving': '正在保存…',
+  'settings_app.disabled_hint': '启用该应用后即可配置。',
+  'settings_app.video_directories_label': '视频文件夹',
+  'settings_app.video_directories_hint': '该群组的影片和剧集所在位置。其外的内容不会出现在「视频」标签页。',
+  'settings_app.music_directories_label': '音乐文件夹',
+  'settings_app.music_directories_hint': '该群组的专辑所在位置。其外的内容不会出现在「音乐」标签页。',
+  'settings_app.photo_directories_label': '照片文件夹',
+  'settings_app.photo_directories_hint': '该群组的相册所在位置。其外的内容不会出现在「照片」标签页。',
+  'settings_app.chat_directory_label': '附件文件夹',
+  'settings_app.chat_directory_hint': '聊天中发送的文件写入位置。必须是可读写的目录。',
+  'settings_app.chat_no_writable_root': '该群组没有可写目录，因此附件已停用。',
+  'settings_app.chat_link_preview_label': '链接预览',
+  'settings_app.chat_link_preview_hint': '当成员发布链接时，节点会抓取该页面的标题和图片。这是从你的机器发往他人所选站点的请求。',
+  'settings_app.tmdb_token_prompt': '在 TMDB 注册以生成你自己的 API 密钥。',
+  'settings_app.tmdb_token_link': '获取密钥',
   'settings_node.roots_offline_hint': '未连接到节点 — 变更将通过本地节点进行，并在其下次重新加载时生效。',
   'settings_node.directories_title': '应用目录',
   'settings_node.directories_hint': '共享文件夹，以及“视频”“音乐”和“照片”应用各自使用哪个（些）作为入口。',