feat(peer): validate manifests before download mutation

Why:
- Remote and UI-echoed file descriptions could reach transaction and storage
  code one entry at a time, so a hostile late path could mutate earlier files.
- Per-file consensus also accepted malformed peer lists and let duplicate rows
  inflate a source's vote.

What:
- Add a complete protocol-7 manifest adapter with catalog-root confinement,
  portable path and alias rules, reserved-path protection, shape and size caps,
  symlink/reparse inspection, and zero-mutation tests.
- Keep download selection in the peer core, validate every peer manifest before
  consensus, and pass only the validated manifest into storage/orchestration.
- Canonicalize locally advertised paths, cap exact chunk receives, and preserve
  the local-only install fast path.
- Record the chosen safety limits and follow-up ownership/catalog decisions.

Test Plan:
- just clippy
- just test
- just frontend-test
- just build
- just fmt (Rust/TOML/Prettier completed; rumdl reports 39 pre-existing issues)
- git diff --cached --check

crates/lanspread-peer/src/lib.rs

@@ -238,14 +238,10 @@ pub enum PeerCommand {
     /// Request the latest peer-advertised file details for an update.
     FetchLatestFromPeers { id: String },
     /// Download game files.
-    DownloadGameFiles {
-        id: String,
-        file_descriptions: Vec<GameFileDescription>,
-    },
+    DownloadGameFiles { id: String },
     /// Download game files with an explicit install policy.
     DownloadGameFilesWithOptions {
         id: String,
-        file_descriptions: Vec<GameFileDescription>,
         install_after_download: bool,
     },
     /// Stream archive-expanded bytes directly into `local/` without keeping root archives.
@@ -458,26 +454,15 @@ async fn handle_peer_commands(
                 handle_get_game_command(ctx, tx_notify_ui, id, GameDetailSource::LatestPeersOnly)
                     .await;
             }
-            PeerCommand::DownloadGameFiles {
-                id,
-                file_descriptions,
-            } => {
-                handle_download_game_files_command(ctx, tx_notify_ui, id, file_descriptions, true)
-                    .await;
+            PeerCommand::DownloadGameFiles { id } => {
+                handle_download_game_files_command(ctx, tx_notify_ui, id, true).await;
             }
             PeerCommand::DownloadGameFilesWithOptions {
                 id,
-                file_descriptions,
                 install_after_download,
             } => {
-                handle_download_game_files_command(
-                    ctx,
-                    tx_notify_ui,
-                    id,
-                    file_descriptions,
-                    install_after_download,
-                )
-                .await;
+                handle_download_game_files_command(ctx, tx_notify_ui, id, install_after_download)
+                    .await;
             }
             PeerCommand::StreamInstallGame { id } => {
                 handlers::handle_stream_install_game_command(ctx, tx_notify_ui, id).await;