wayland: lang keys for the staged portal failures

Five keys, appended to `template.rs` and to every `src/lang/*.rs`. `it.rs` gets
empty values, as AGENTS.md requires -- it is maintained by hand by its
translator. No `en.rs` entries: each key is already its own English display
text, which is also what an older peer falls back to.

Two carry a `{}`: the portal's response code, and the name of the GStreamer
element that could not be created. `lang.rs`'s `extract_placeholder` resolves a
key by replacing the first `{...}` with `{}`, which is why the server sends the
value still inside the braces and why the scrap side strips braces out of any
detail before it gets there.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EZ49AbZJYfm8NTp5yDPMab

src/lang/ja.rs

@@ -770,5 +770,10 @@ pub static ref T: std::collections::HashMap<&'static str, &'static str> =
         ("port-forward-mux-tip", "1 つのポート転送のすべての接続を、相手への 1 本の接続にまとめます。接続ごとに接続とログインをやり直しません。"),
         ("Enable WebRTC P2P connection", "WebRTC P2P 接続を有効化する"),
         ("Enable TCP hole punching", "TCP ホールパンチを有効化する"),
+        ("The screen sharing request was declined on the remote device", "リモート端末で画面共有の要求が拒否されました"),
+        ("No one responded to the screen sharing request on the remote device", "リモート端末で画面共有の要求に誰も応答しませんでした"),
+        ("The XDG Desktop Portal ended the screen sharing request ({})", "XDG Desktop Portal が画面共有の要求を終了しました ({})"),
+        ("The XDG Desktop Portal returned no screen to capture, the PipeWire library may be too old", "XDG Desktop Portal がキャプチャ対象の画面を返しませんでした。PipeWire ライブラリが古すぎる可能性があります"),
+        ("A GStreamer plugin needed for screen capture is missing ({})", "画面キャプチャに必要な GStreamer プラグインがありません ({})"),
     ].iter().cloned().collect();
 }