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"