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, 78 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 8df7700..785b926 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -85,6 +85,7 @@ const ADMIN_OP_TYPES = new Set([
   'musicbrainz_enabled', 'file_delete', 'dir_delete',
   'apps_enabled', 'set_scan_settings', 'member_revoke',
   'root_add', 'root_remove', 'root_update', 'root_eject', 'root_plug',
+  'app_directories', 'chat_directory', 'chat_link_preview',
   'member_unpin', 'gek_rotate', 'group_attach',
   'group_detach', 'invite_create',
 ]);
@@ -335,6 +336,9 @@ class MeshBayTransport {
   set onUploadPolicy(fn) { this._onUploadPolicy = fn; }
   set onRootsChanged(fn) { this._onRootsChanged = fn; }
   set onAppsEnabled(fn) { this._onAppsEnabled = fn; }
+  set onAppDirectories(fn) { this._onAppDirectories = fn; }
+  set onChatDirectory(fn) { this._onChatDirectory = fn; }
+  set onChatLinkPreview(fn) { this._onChatLinkPreview = fn; }
   set onTmdbConfig(fn) { this._onTmdbConfig = fn; }
   set onTmdbEnabled(fn) { this._onTmdbEnabled = fn; }
   set onVideoRoot(fn) { this._onVideoRoot = fn; }
@@ -1178,6 +1182,68 @@ class MeshBayTransport {
   }
 
   /**
+   * Point an application at folder(s) inside the group's shared directories.
+   *
+   * One method for every app, keyed by the app's registry name — the same
+   * generic op the node grew for the same reason (docs/refactor-groups.md
+   * §1.6). `setVideoRoot`, `setAudioRoot` and `setPhotoRoots` are still here
+   * and still work; nothing new should call them.
+   *
+   * The subject names the app as well as the paths, because an operator shown
+   * "Media/Films" alone cannot tell which application is about to be pointed
+   * at it, and two apps' challenges would otherwise be indistinguishable.
+   * Cleaned and sorted the same way the node does, so both sides build the
+   * same bytes to sign.
+   */
+  async setAppDirectories(appKey, directories, signFn) {
+    const clean = [...new Set(
+      (directories || []).map((d) => (d || '').replace(/^\/+|\/+$/g, '')).filter(Boolean),
+    )].sort();
+    const msg = await this._sendAndWait({
+      type: 'app_directories', v: '1.1', app: appKey, directories: clean,
+    });
+    if (msg.type === 'error') throw new Error(msg.detail);
+    if (msg.type === 'admin_challenge') {
+      return this._authorizeAdminOp(
+        msg, 'app_directories', `${appKey}:${clean.join(',')}`, signFn);
+    }
+    return msg;
+  }
+
+  /**
+   * Where chat attachments are written.
+   *
+   * Its own message rather than `setAppDirectories('chat', ...)`: this one is
+   * a destination, and the node refuses a read-only root for it. A caller
+   * reaching for the generic form would get a refusal it has no reason to
+   * expect, so the difference is in the name.
+   */
+  async setChatDirectory(path, signFn) {
+    const clean = (path || '').replace(/^\/+|\/+$/g, '');
+    const msg = await this._sendAndWait({
+      type: 'chat_directory', v: '1.1', path: clean,
+    });
+    if (msg.type === 'error') throw new Error(msg.detail);
+    if (msg.type === 'admin_challenge') {
+      return this._authorizeAdminOp(msg, 'chat_directory', clean, signFn);
+    }
+    return msg;
+  }
+
+  /** Whether the node unfurls links members post in this group's chat. */
+  async setChatLinkPreview(enabled, signFn) {
+    const msg = await this._sendAndWait({
+      type: 'chat_link_preview', v: '1.1', enabled: Boolean(enabled),
+    });
+    if (msg.type === 'error') throw new Error(msg.detail);
+    if (msg.type === 'admin_challenge') {
+      return this._authorizeAdminOp(
+        msg, 'chat_link_preview', enabled ? 'on' : 'off', signFn);
+    }
+    return msg;
+  }
+
+  /**
    * MusicBrainz metadata for one track (Music app, docs/musicbay.md §4.3)
    * — same shape as fetchMediaMeta, minus a season/episode concept:
    * album-level (release), resolved from the track's own artist/album
@@ -2291,6 +2357,18 @@ class MeshBayTransport {
       this._onAppsEnabled(msg.apps || []);
     }
 
+    // An application was pointed at different folders. One handler for every
+    // app — the callback is given the app's name and decides.
+    if (msg.type === 'app_directories_ack' && this._onAppDirectories) {
+      this._onAppDirectories(msg.app, msg.directories || []);
+    }
+    if (msg.type === 'chat_directory_ack' && this._onChatDirectory) {
+      this._onChatDirectory(msg.path || '');
+    }
+    if (msg.type === 'chat_link_preview_ack' && this._onChatLinkPreview) {
+      this._onChatLinkPreview(Boolean(msg.enabled));
+    }
+
     // Node-wide (not per-group) — the operator supplied/cleared a custom
     // token, or changed the query language. `token_customized` only says
     // whether one is set, never the token itself.