fix(worker): harden CLI injection, stuck-Running, chain wedge, and Fail guard

1. ArgumentList (fix injection): ClaudeArgsBuilder.Build() now returns
   IReadOnlyList<string>; ClaudeProcess populates ProcessStartInfo.ArgumentList
   instead of Arguments, so values like system prompts are never shell-split.
   DailyPrepPrompt, RefinePrompt, and WeekReportService migrated similarly.
   All IClaudeProcess fakes updated.

2. ContinueAsync exception guard: wrap RunOnceAsync in try/catch matching
   the RunAsync pattern so an unexpected exception never leaves the task
   stuck in Running status.

3. Planning chain cascade: OnChildFinishedAsync now calls CancelAsync on
   the immediate blocked successor when a child fails or is cancelled,
   triggering a recursive cascade that clears the entire remaining chain
   instead of leaving it wedged.

4. FailAsync guard: restrict valid source states to Running and Queued;
   WaitingForReview -> Failed is now rejected, preventing an invalid
   transition that could corrupt the review workflow.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Worker/Runner/ClaudeProcess.cs

@@ -18,7 +18,7 @@ public sealed class ClaudeProcess : IClaudeProcess
     }
 
     public async Task<RunResult> RunAsync(
-        string arguments,
+        IReadOnlyList<string> arguments,
         string prompt,
         string workingDirectory,
         Func<string, Task> onStdoutLine,
@@ -27,7 +27,6 @@ public sealed class ClaudeProcess : IClaudeProcess
         var psi = new ProcessStartInfo
         {
             FileName = _cfg.ClaudeBin,
-            Arguments = arguments,
             WorkingDirectory = workingDirectory,
             RedirectStandardInput = true,
             RedirectStandardOutput = true,
@@ -37,6 +36,8 @@ public sealed class ClaudeProcess : IClaudeProcess
             StandardOutputEncoding = Encoding.UTF8,
             StandardErrorEncoding = Encoding.UTF8,
         };
+        foreach (var arg in arguments)
+            psi.ArgumentList.Add(arg);
 
         using var process = new Process { StartInfo = psi };
         process.Start();