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>

tests/ClaudeDo.Worker.Tests/Refine/RefineRunnerTests.cs

@@ -105,7 +105,7 @@ internal sealed class RecordingClaudeProcess : IClaudeProcess
 
     public RecordingClaudeProcess(bool success) => _success = success;
 
-    public Task<RunResult> RunAsync(string arguments, string prompt, string workingDirectory,
+    public Task<RunResult> RunAsync(IReadOnlyList<string> arguments, string prompt, string workingDirectory,
         Func<string, Task> onStdoutLine, CancellationToken ct)
     {
         Interlocked.Increment(ref _callCount);