feat(worker): in-app interactive session service, replacing the wt terminal launch

InteractiveSessionService resolves a task's list working dir + seeded prompt,
spawns a StreamingClaudeSession (claude stream-json in the list dir, model+auto
as before), registers it in LiveSessionRegistry, streams output over TaskMessage,
and broadcasts InteractiveSessionStarted/Ended (an exit watcher fires Ended). The
hub's OpenInteractiveTerminalAsync now starts this in-app session; SendInteractiveMessage
and StopInteractiveSession route to it. The external Windows-Terminal interactive
launch (LaunchInteractiveAsync / InteractiveLaunchContext / OpenInteractiveAsync) is
removed; planning sessions keep their terminal launch.

src/ClaudeDo.Worker/Planning/WindowsTerminalLauncher.cs

@@ -74,29 +74,6 @@ public sealed class WindowsTerminalLauncher : ITerminalLauncher
         return Task.CompletedTask;
     }
 
-    public Task LaunchInteractiveAsync(InteractiveLaunchContext ctx, CancellationToken cancellationToken)
-    {
-        if (!Directory.Exists(ctx.WorkingDir))
-            throw new TerminalLaunchException($"Working directory does not exist: {ctx.WorkingDir}");
-
-        var resolvedWt = ResolveWtOrThrow();
-        var resolvedClaude = ResolveClaudeOrThrow();
-
-        var command = BuildPwshCommand(resolvedClaude, new[]
-        {
-            "--model", Model,
-            "--permission-mode", "auto",
-        }, appendPrompt: true);
-
-        StartInWindowsTerminal(resolvedWt, ctx.WorkingDir, command, env =>
-        {
-            env["MAX_THINKING_TOKENS"] = "20000";
-            env[PromptEnvVar] = ctx.InitialPrompt;
-        });
-
-        return Task.CompletedTask;
-    }
-
     public Task LaunchPlanningResumeAsync(PlanningSessionResumeContext ctx, CancellationToken cancellationToken)
     {
         if (!Directory.Exists(ctx.WorkingDir))