fix(worker): resolve claude CLI shims (.cmd/.bat) not just .exe on PATH

UseShellExecute=false only appends .exe when searching PATH, so an
npm-installed claude.cmd was never found even though it works from a shell.
Adds a shared ExecutableResolver in ClaudeDo.Data (PATH/PATHEXT aware, with
known npm/claude install-dir fallbacks) and wires it into ClaudeCliPreflight
and ClaudeProcess; shims are launched via cmd.exe /c.

src/ClaudeDo.Worker/Runner/ClaudeProcess.cs

@@ -1,5 +1,6 @@
 using System.Diagnostics;
 using System.Text;
+using ClaudeDo.Data.Environment;
 using ClaudeDo.Worker.Config;
 
 namespace ClaudeDo.Worker.Runner;
@@ -24,9 +25,11 @@ public sealed class ClaudeProcess : IClaudeProcess
         Func<string, Task> onStdoutLine,
         CancellationToken ct)
     {
+        var resolved = ExecutableResolver.Resolve(_cfg.ClaudeBin)
+            ?? throw new InvalidOperationException($"'{_cfg.ClaudeBin}' not found on PATH.");
+
         var psi = new ProcessStartInfo
         {
-            FileName = _cfg.ClaudeBin,
             WorkingDirectory = workingDirectory,
             RedirectStandardInput = true,
             RedirectStandardOutput = true,
@@ -36,6 +39,20 @@ public sealed class ClaudeProcess : IClaudeProcess
             StandardOutputEncoding = Encoding.UTF8,
             StandardErrorEncoding = Encoding.UTF8,
         };
+
+        // A shim (.cmd/.bat) can't be launched directly with UseShellExecute=false;
+        // route it through cmd.exe /c so the real interpreter starts the target.
+        if (resolved.IsShim)
+        {
+            psi.FileName = "cmd.exe";
+            psi.ArgumentList.Add("/c");
+            psi.ArgumentList.Add(resolved.Path);
+        }
+        else
+        {
+            psi.FileName = resolved.Path;
+        }
+
         foreach (var arg in arguments)
             psi.ArgumentList.Add(arg);