feat(node,hub): add Videos group app (poster grid, flat list, TMDB metadata)

Implements docs/mediacenter.md: a "Videos" group application built on the
existing files index rather than a separate catalogue. On the node side,
new indexer enrichment (technical probe, filename/season parsing, thumbnail
generation) runs per-file once an operator has chosen a video_root for the
group, plus a TMDB client for on-demand poster/metadata lookups (never
client-side, thumbnails delivered over the existing chunk path). On the hub
side, a new video-app.js renders a lazily-mounted poster grid or a
thumbnail-only flat list, with TMDB entirely optional per group.

Along the way: the global apps registry now drives Settings' default-tab
picker instead of a hardcoded list, and the video_root is configured from
group Settings (like uploads) rather than from Files, with the node
refusing to run any TMDB/thumbnail work until one is set.

Fixes several bugs found via live testing against a real library, notably
a race between two effects writing the same "image ready" state that could
leave a poster grid spinning forever on a same-tab revisit — see
mediacenter.md §5.4 for the full account of each one.

1 files changed, 36 insertions, 0 deletions

diff --git a/packages/meshbay-common/src/meshbay_common/protocol.py b/packages/meshbay-common/src/meshbay_common/protocol.py
index e1bfb8e..246bd00 100644
--- a/packages/meshbay-common/src/meshbay_common/protocol.py
+++ b/packages/meshbay-common/src/meshbay_common/protocol.py
@@ -90,6 +90,12 @@ class MNP:
     APPS_ENABLED_ACK     = "apps_enabled_ack"
     SET_SCAN_SETTINGS     = "set_scan_settings"     # operator → node: reconcile/debounce timing
     SET_SCAN_SETTINGS_ACK = "set_scan_settings_ack"
+    MEDIA_META_REQ        = "media_meta_req"        # client → node: TMDB metadata for a path
+    MEDIA_META_RESP       = "media_meta_resp"       # node → client: TMDB metadata (or none)
+    VIDEO_ROOT            = "video_root"             # operator → node: which folder is the Videos entry point
+    VIDEO_ROOT_ACK        = "video_root_ack"
+    TMDB_CONFIG           = "tmdb_config"            # operator → node: enable/disable TMDB, set token
+    TMDB_CONFIG_ACK       = "tmdb_config_ack"        # node → everyone: new TMDB config (never the token)
     # Device linking. A new device files a request bound to a code it displays;
     # an already-pinned device of the same account approves it. Neither the hub
     # nor the node can produce the countersignature.
@@ -141,6 +147,30 @@ class IndexEntry:
     thumb_hash: str | None = None  # blake3 of thumbnail
     uploader_id: str | None = None  # user_id of who uploaded (None = pre-existing on disk)
     uploader_pk: str | None = None  # Ed25519 public key of uploader (base64 raw 32 bytes)
+    width:      int | None = None  # pixels, video only
+    height:     int | None = None  # pixels, video only
+    display_title: str | None = None  # parsed or cleaned-filename title, Videos app
+    season:     int | None = None  # parsed season number, Videos app
+    episode:    int | None = None  # parsed episode number, Videos app
+
+
+def index_entry_wire(e: IndexEntry) -> dict:
+    """
+    The wire-dict shape used by INDEX_SYNC/INDEX_DELTA hand-built messages
+    (as opposed to GroupIndex.serialize()'s asdict() encoding of the whole
+    index). Centralized so the three call sites that build these
+    (webrtc_server._do_index_sync, daemon._broadcast_index_change's two
+    branches) can't drift from each other as fields are added.
+    """
+    return {
+        "id": e.id, "name": e.name, "path": e.path,
+        "size": e.size, "type": e.type, "added_at": e.added_at,
+        "uploader_id": e.uploader_id,
+        "duration": e.duration, "thumb_hash": e.thumb_hash,
+        "width": e.width, "height": e.height,
+        "display_title": e.display_title,
+        "season": e.season, "episode": e.episode,
+    }
 
 
 @dataclass
@@ -149,6 +179,12 @@ class IndexDelta:
     version:      int
     additions:    list[IndexEntry] = field(default_factory=list)
     deletions:    list[str] = field(default_factory=list)  # list of ids
+    # Same id as before (same file, same content hash), different field
+    # values — e.g. the Videos app's async enrichment filling in duration/
+    # thumb_hash/etc. after the file was already indexed with hash+size only.
+    # A distinct list from `additions`: `GroupIndex.diff()` only ever adds an
+    # id here once it has already appeared unchanged in a prior snapshot.
+    updates:      list[IndexEntry] = field(default_factory=list)
 
 
 # ── Chunk request/response ────────────────────────────────────────────────────