feat(interactive): worker launch-spec for embedded ConPTY sessions

Adds InteractiveLaunchSpecService + GetInteractiveLaunchSpec hub method that
prepares a task worktree (session-skills seeding, run env) and returns a
LaunchSpec {cwd,exe,args,env} for a UI-hosted ConPTY terminal. Reuses
ISessionSkillSeeder, TaskRunner.UnionSkillNames, and WindowsTerminalLauncher
resume-arg/resolve logic. Guards mirror ResumeTaskInTerminal; a never-run task
yields a fresh-start spec instead of an error.

src/ClaudeDo.Worker/Planning/WindowsTerminalLauncher.cs

@@ -106,7 +106,12 @@ public sealed class WindowsTerminalLauncher : ITerminalLauncher
     // Resumes a session by id in default (interactive) permission mode: the user drives
     // tool approvals in the terminal, unlike planning which pins --permission-mode plan.
     internal static string BuildResumeCommand(string claudePath, string claudeSessionId) =>
-        BuildPwshCommand(claudePath, new[] { "--resume", claudeSessionId });
+        BuildPwshCommand(claudePath, BuildResumeArgs(claudeSessionId));
+
+    // The raw claude CLI args for a --resume launch, shared with InteractiveLaunchSpecService
+    // (which needs the bare Exe/Args pair for a ConPTY host, not a wrapped pwsh command line).
+    internal static IReadOnlyList<string> BuildResumeArgs(string claudeSessionId) =>
+        new[] { "--resume", claudeSessionId };
 
     // Builds the PowerShell command that launches an interactive planning session.
     // Arg order matters: variadic flags (--allowedTools, --add-dir) come first; the
@@ -174,7 +179,9 @@ public sealed class WindowsTerminalLauncher : ITerminalLauncher
             ?? throw new TerminalLaunchException("Failed to start Windows Terminal process.");
     }
 
-    private static string? Resolve(string pathOrName)
+    // Not private: reused by InteractiveLaunchSpecService to resolve the claude executable
+    // for a ConPTY-hosted launch spec the same way a wt-launched terminal resolves it.
+    internal static string? Resolve(string pathOrName)
     {
         if (File.Exists(pathOrName))
             return pathOrName;