Let a session's transport say what it negotiated

ISshConnection and ISftpSession both carry Cipher now — the server-to-client
algorithm off SSH.NET's own ConnectionInfo, captured once because a rekey is
not an event that library raises — and TerminalWorkspace.GetSessionFacts hands
that plus the host key's algorithm back per session, without ever handing over
the connection itself. Nothing reads either yet; the status bar that will is
the next commit.

src/DodoSSH.Client.Terminal/TerminalWorkspace.cs

@@ -37,6 +37,18 @@ public sealed class TerminalSessionEndedEventArgs(uint sessionId) : EventArgs
     public uint SessionId { get; } = sessionId;
 }
 
+/// <summary>
+/// The negotiated cipher and host-key algorithm for one live session.
+/// </summary>
+/// <param name="Cipher">The server-to-client encryption algorithm; see <see cref="ISshConnection.Cipher"/>.</param>
+/// <param name="HostKeyAlgorithm">The host key's algorithm, e.g. <c>ssh-ed25519</c>.</param>
+/// <remarks>
+/// Two facts rather than the whole <see cref="ISshConnection"/>, because that is all a caller outside this
+/// assembly has any business reading off a session it does not own — everything else on the connection
+/// (disposal, the shell) belongs to the workspace alone. See <see cref="TerminalWorkspace.GetSessionFacts"/>.
+/// </remarks>
+public sealed record SessionFacts(string Cipher, string HostKeyAlgorithm);
+
 /// <summary>The renderer asking for a different font size.</summary>
 /// <param name="step">
 /// How far to move, in points of font size, or zero to go back to the default. It is a step rather than a
@@ -180,6 +192,37 @@ public sealed class TerminalWorkspace : IAsyncDisposable
         }
     }
 
+    /// <summary>
+    /// The negotiated cipher and host-key algorithm for one live session, or null when the id names no
+    /// session this workspace still has open.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Additive, and deliberately narrow: the caller this exists for — the shell's own connect path, which
+    /// wants these two facts for its status bar — has no other business with a session it does not own, and a
+    /// method that handed back the <see cref="ISshConnection"/> itself would have handed over the shell,
+    /// disposal and all, to code that already goes through <see cref="CloseSessionAsync"/> for that.
+    /// </para>
+    /// <para>
+    /// "No session this workspace still has open" covers two different absences the same way
+    /// <see cref="IsSessionLive"/> already does: an id this workspace never issued, and one whose shell has
+    /// already ended but whose entry has not been removed yet. Both are "nothing to report" to a caller
+    /// asking what a session's transport looks like right now.
+    /// </para>
+    /// </remarks>
+    public SessionFacts? GetSessionFacts(uint sessionId)
+    {
+        lock (sessionGate)
+        {
+            if (!sessions.TryGetValue(sessionId, out var session) || session.Run.IsCompleted)
+            {
+                return null;
+            }
+
+            return new SessionFacts(session.Connection.Cipher, session.Connection.HostKey.Algorithm);
+        }
+    }
+
     /// <summary>
     /// Raised with the session id when a shell ends on its own.
     /// </summary>