feat(peer): remove downloaded game files safely

Downloaded but uninstalled games can still occupy significant disk space. Add a
separate removal path for that state instead of overloading uninstall, which is
reserved for deleting only `local/` installs.

The peer runtime now exposes `RemoveDownloadedGame` with matching lifecycle
and active-operation events. The filesystem delete is intentionally strict: the
id must be a catalog game and a single path component, the target must be a
direct child of the configured game directory, the root must not be a symlink,
it must have a regular root-level `version.ini`, and it must not contain
`local/`, `.local.installing/`, or `.local.backup/`. Only then do we recursively
remove the game root.

The Tauri bridge exposes this as `remove_downloaded_game`, the frontend shows a
matching danger action only for downloaded-but-uninstalled games, and a
confirmation dialog warns that re-downloading can take a long time.

Test Plan:
- git diff --check
- just fmt
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= just test
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= just clippy
- RUSTC_WRAPPER= CARGO_BUILD_RUSTC_WRAPPER= just build

Refs: user redesign nitpick about removing downloaded uninstalled games

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

@@ -5,7 +5,7 @@ import { StateChip } from '../StateChip';
 import { ActionButton } from '../ActionButton';
 
 import { Game } from '../../lib/types';
-import { deriveState } from '../../lib/gameState';
+import { deriveState, isInProgress } from '../../lib/gameState';
 import { formatBytes, formatEtiVersion, formatPlayers } from '../../lib/format';
 
 interface Props {
@@ -14,6 +14,7 @@ interface Props {
     onClose: () => void;
     onPrimary: (game: Game) => void;
     onUninstall: (game: Game) => void;
+    onRemoveDownload: (game: Game) => void;
 }
 
 const tagsFromGame = (game: Game): string[] => {
@@ -33,8 +34,18 @@ const statusLabelFor = (game: Game): string => {
     }
 };
 
-export const GameDetailModal = ({ game, thumbnailUrl, onClose, onPrimary, onUninstall }: Props) => {
+export const GameDetailModal = ({
+    game,
+    thumbnailUrl,
+    onClose,
+    onPrimary,
+    onUninstall,
+    onRemoveDownload,
+}: Props) => {
     const tags = tagsFromGame(game);
+    const canRemoveDownload = game.downloaded
+        && !game.installed
+        && !isInProgress(game.install_status);
     return (
         <Modal onClose={onClose}>
             <button className="modal-close" type="button" onClick={onClose} aria-label="Close">
@@ -102,6 +113,16 @@ export const GameDetailModal = ({ game, thumbnailUrl, onClose, onPrimary, onUnin
                             <span>Uninstall</span>
                         </button>
                     )}
+                    {canRemoveDownload && (
+                        <button
+                            type="button"
+                            className="ghost-btn ghost-danger"
+                            onClick={() => onRemoveDownload(game)}
+                        >
+                            <Icon.trash />
+                            <span>Remove files</span>
+                        </button>
+                    )}
                 </div>
             </div>
         </Modal>