feat(tauri): add low-disk streamed install action

NEXT_STEPS item 1 called out that streamed install was still CLI-only
because the Tauri app started the peer with no stream provider. Users can now
choose an explicit "Low disk install" action from the game detail modal for
remote-only games instead of taking the default archive-preserving download
path.

The GUI command queues a normal peer detail fetch first so the peer database
has the file metadata needed for source validation. A small pending handoff in
Tauri routes the resulting GotGameFiles event into StreamInstallGame instead
of DownloadGameFiles, and clears that pending state on no-peer or download
failure events. This keeps the existing download continuation untouched for
the default action.

The external unrar stream provider moved from the CLI harness into
lanspread-peer so CLI and Tauri use the same implementation. Tauri resolves
the bundled unrar sidecar path and injects that provider at peer startup;
falling back to the noop provider keeps peer startup alive if the sidecar
cannot be resolved, while the streamed install operation still fails safely.

Test Plan:
- just fmt
- just test
- just frontend-test
- just clippy
- just build
- git diff --check

Refs: NEXT_STEPS.md item 1

crates/lanspread-tauri-deno-ts/src/components/modals/GameDetailModal.tsx

@@ -5,7 +5,7 @@ import { StateChip } from '../StateChip';
 import { ActionButton } from '../ActionButton';
 
 import { Game, InstallStatus } from '../../lib/types';
-import { deriveState, hasNewerLocalVersion, isInProgress } from '../../lib/gameState';
+import { canStreamInstall, deriveState, hasNewerLocalVersion, isInProgress } from '../../lib/gameState';
 import { formatBytes, formatEtiVersion, formatPlayers } from '../../lib/format';
 
 interface Props {
@@ -13,6 +13,7 @@ interface Props {
     thumbnailUrl: string | null;
     onClose: () => void;
     onPrimary: (game: Game) => void;
+    onStreamInstall: (game: Game) => void;
     onUninstall: (game: Game) => void;
     onRemoveDownload: (game: Game) => void;
     onCancelDownload: (game: Game) => void;
@@ -43,6 +44,7 @@ export const GameDetailModal = ({
     thumbnailUrl,
     onClose,
     onPrimary,
+    onStreamInstall,
     onUninstall,
     onRemoveDownload,
     onCancelDownload,
@@ -55,6 +57,7 @@ export const GameDetailModal = ({
     const canRemoveDownload = game.downloaded
         && !game.installed
         && !isInProgress(game.install_status);
+    const showStreamInstall = canStreamInstall(game);
     const canViewFiles = game.downloaded
         || game.installed
         || game.install_status === InstallStatus.Downloading
@@ -133,6 +136,17 @@ export const GameDetailModal = ({
                         onClick={() => onPrimary(game)}
                         onCancelDownload={onCancelDownload}
                     />
+                    {showStreamInstall && (
+                        <button
+                            type="button"
+                            className="ghost-btn"
+                            title="Install without keeping archive files"
+                            onClick={() => onStreamInstall(game)}
+                        >
+                            <Icon.install />
+                            <span>Low disk install</span>
+                        </button>
+                    )}
                     {game.installed && game.can_host_server === true && (
                         <button
                             type="button"

crates/lanspread-tauri-deno-ts/src/hooks/useGameActions.ts

@@ -9,6 +9,7 @@ export interface GameActions {
     play: (id: string) => Promise<void>;
     startServer: (id: string) => Promise<void>;
     install: (id: string) => Promise<void>;
+    streamInstall: (id: string) => Promise<void>;
     update: (id: string) => Promise<void>;
     uninstall: (id: string) => Promise<void>;
     removeDownload: (id: string) => Promise<void>;
@@ -68,6 +69,15 @@ export const useGameActions = (
         }
     }, [games, settings.language, settings.username]);
 
+    const streamInstall = useCallback(async (id: string) => {
+        try {
+            const success = await invoke<boolean>('stream_install_game', { id });
+            if (success) games.markChecking(id);
+        } catch (err) {
+            console.error('stream_install_game failed:', err);
+        }
+    }, [games]);
+
     const update = useCallback(async (id: string) => {
         try {
             const game = games.games.find(item => item.id === id);
@@ -129,5 +139,15 @@ export const useGameActions = (
         }
     }, []);
 
-    return { play, startServer, install, update, uninstall, removeDownload, cancelDownload, viewFiles };
+    return {
+        play,
+        startServer,
+        install,
+        streamInstall,
+        update,
+        uninstall,
+        removeDownload,
+        cancelDownload,
+        viewFiles,
+    };
 };

crates/lanspread-tauri-deno-ts/src/lib/gameState.ts

@@ -114,6 +114,12 @@ export const needsUpdate = (game: Game): boolean => {
     return (compareVersionStamps(game.eti_game_version, game.local_version) ?? 0) > 0;
 };
 
+export const canStreamInstall = (game: Game): boolean =>
+    !game.downloaded
+    && !game.installed
+    && game.peer_count > 0
+    && !isInProgress(game.install_status);
+
 /** What pressing the card's main action button should do, given the state. */
 export type PrimaryAction = 'play' | 'install' | 'update' | 'download' | 'busy' | 'disabled';
 

crates/lanspread-tauri-deno-ts/src/windows/MainWindow.tsx

@@ -192,6 +192,7 @@ export const MainWindow = () => {
                     thumbnailUrl={thumbnails.get(openGame.id)}
                     onClose={() => setOpenGameId(null)}
                     onPrimary={handlePrimary}
+                    onStreamInstall={(g) => actions.streamInstall(g.id)}
                     onUninstall={handleUninstall}
                     onRemoveDownload={handleRemoveDownload}
                     onCancelDownload={(g) => actions.cancelDownload(g.id)}