fix(worker): strip trailing separator from the list repo in ConPTY launch args

The ConPTY host flattens LaunchSpec.Args into one Windows command line and quotes
each token, so a list working dir stored as "C:\repo\" produced the token
"C:\repo\" -- whose trailing backslash escapes its own closing quote. Everything
after it collapsed into --add-dir's variadic list, including
--append-system-prompt-file and the positional kickoff, so "Let Claude handle it"
opened a session with no prompt at all and the CLI warned that brief.md is not a
directory. Only user-supplied working dirs can carry a trailing separator; the
session dirs the worker builds never do.

src/ClaudeDo.Worker/Runner/InteractiveLaunchSpecService.cs

@@ -223,6 +223,7 @@ public sealed class InteractiveLaunchSpecService : IInteractiveLaunchSpecService
         var repoDir = list.WorkingDir;
         if (string.IsNullOrEmpty(repoDir) || !Directory.Exists(repoDir))
             throw new InvalidOperationException($"list '{list.Name}' has no existing working directory");
+        repoDir = TrimTrailingSeparator(repoDir);
 
         var briefLines = new List<string>();
         foreach (var id in taskIds)
@@ -300,6 +301,7 @@ public sealed class InteractiveLaunchSpecService : IInteractiveLaunchSpecService
         var repoDir = list.WorkingDir;
         if (string.IsNullOrEmpty(repoDir) || !Directory.Exists(repoDir))
             throw new InvalidOperationException($"list '{list.Name}' has no existing working directory");
+        repoDir = TrimTrailingSeparator(repoDir);
 
         var briefLines = new List<string>();
         foreach (var id in survivingTaskIds)
@@ -349,6 +351,19 @@ public sealed class InteractiveLaunchSpecService : IInteractiveLaunchSpecService
         return new LaunchSpec(repoDir, resolvedClaude, args, env);
     }
 
+    // Strips a trailing directory separator off a path bound for the CLI argument list. The ConPTY
+    // host flattens Args into ONE Windows command line and quotes each token, so a token ending in
+    // '\' escapes its own closing quote ("C:\repo\" parses as C:\repo" ...) and every following
+    // argument is absorbed into the preceding variadic flag -- for a list handler that means
+    // --add-dir swallows --append-system-prompt-file AND the positional kickoff, and the session
+    // opens with no prompt at all. Only user-supplied list working dirs can carry one; the session
+    // dirs we build never do. A bare root ("C:\", "/") is all separator and is left untouched.
+    private static string TrimTrailingSeparator(string dir)
+    {
+        var trimmed = dir.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        return trimmed.Length == 0 || trimmed.EndsWith(':') ? dir : trimmed;
+    }
+
     // Renders one task as a brief list item. A description can itself be arbitrary Markdown
     // (headings, lists, fenced code) — those must not merge into the brief's own task list, so
     // the description is placed in a fenced code block indented to the list item's continuation