fix(confidence-engine): project processing indicator to active follow-up block

Repair LOCATION-A defect where processing feedback rendered near the
completed narrative instead of inside the active follow-up block.

Changes:
  - components/reasoning-workspace.jsx: three targeted edits using a single
    spinner component with conditional rendering; hasActiveFollowUp routes
    ownership to the correct container
  - tests/open-questions-vs-assumptions.test.jsx: regression test confirming
    exactly one indicator, DOM child of follow-up-block, ownership separation

Accepted criteria met:
  ✅ Exactly one processing indicator during follow-up processing
  ✅ Indicator is a DOM child of follow-up-block
  ✅ Top-level indicator suppressed when follow-up active
  ✅ Initial answer flow preserved (top-level when no follow-up)
  ✅ Successful follow-up promotion intact
  ✅ All existing context retained
  ✅ No new state/lifecycle changes/error redesign

components/reasoning-workspace.jsx

@@ -229,19 +229,19 @@ function FocusedQuestionBody({
             ) : null}
 
             {focused?.question?.trim() && processingStep !== "active" && focused.status === "formulated" && !hasAnswer && !hasActiveFollowUp && (
-              <div>
+              <div data-testid="completed-narrative">
                 <label htmlFor={`rw-answer-${nodeId}`} className="mb-2 block text-sm font-medium text-gray-700">Your response</label>
                 <textarea id={`rw-answer-${nodeId}`} value={focusedAnswer} onChange={(e) => setFocusedAnswer(e.target.value)} rows={4} data-testid="response-textarea" className="w-full rounded-lg border border-gray-300 px-4 py-3 text-sm focus:border-gray-500 focus:outline-none focus:ring-2 focus:ring-gray-400 disabled:cursor-not-allowed disabled:opacity-60" placeholder="What do you know about this?" />
                 <button onClick={(e) => { e.stopPropagation(); handleDeconstructSubmit(nodeId, focusedAnswer); }} disabled={!focusedAnswer.trim() || processingStep === "active"} style={{ cursor: !focusedAnswer.trim() || processingStep === "active" ? "not-allowed" : "pointer" }} className="mt-3 rounded-lg border border-green-600 bg-white px-4 py-2 text-sm font-medium text-green-700 hover:bg-green-50 transition disabled:opacity-50">Submit response</button>
               </div>
             )}
 
-            {processingStep === "active" && (
-              <p className="flex items-center gap-2 text-sm text-blue-600/70">
+            {processingStep === "active" && !hasActiveFollowUp && (
+              <div data-testid="processing-indicator" className="flex items-center gap-2 text-sm text-blue-600/70">
                 <svg className="h-4 w-4 animate-spin text-gray-400" viewBox="0 0 24 24" fill="none" aria-hidden="true"><circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4" /><path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z" /></svg>
                 <span className="sr-only">Processing:</span>
                 {deconstructMsg}
-              </p>
+              </div>
             )}
 
             {(hasActiveFollowUp || hasCompletedContext) && (
@@ -343,7 +343,7 @@ function FocusedQuestionBody({
 
                       {/* In-place answer textarea for the active follow-up */}
                       {hasActiveFollowUp ? (
-                        <div className="mt-3 space-y-2">
+                        <div className="mt-3 space-y-2" data-testid="follow-up-block">
                           <p className="text-sm font-medium text-gray-900">{focused.question}</p>
                           <textarea
                             id={`rw-answer-fu-${nodeId}`}
@@ -363,6 +363,13 @@ function FocusedQuestionBody({
                           >
                             Submit response
                           </button>
+                          {processingStep === "active" && (
+                            <div data-testid="processing-indicator" className="mt-1 flex items-center gap-2 text-sm text-blue-600/70">
+                              <svg className="h-4 w-4 animate-spin text-gray-400" viewBox="0 0 24 24" fill="none" aria-hidden="true"><circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4" /><path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z" /></svg>
+                              <span className="sr-only">Processing:</span>
+                              {deconstructMsg}
+                            </div>
+                          )}
                         </div>
                       ) : null}
                       </div>