feat: AI RCA draft assistant in investigation form

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FFDuBhMKvoWjrWT3ZnGmmr

components/incidents/investigation-form.tsx

@@ -40,6 +40,7 @@ export function InvestigationForm({ incidentId, existingInvestigationId }: Props
   const [complete, setComplete] = useState(false)
   const [saving, setSaving] = useState(false)
   const [error, setError] = useState<string | null>(null)
+  const [aiDraftLoading, setAiDraftLoading] = useState(false)
 
   function addWhyStep() {
     if (fiveWhy.length >= 5) return
@@ -57,6 +58,31 @@ export function InvestigationForm({ incidentId, existingInvestigationId }: Props
     setFishbone(fishbone.map((c, i) => i === catIdx ? { ...c, causes: [...c.causes, ''] } : c))
   }
 
+  async function getAiDraft() {
+    setAiDraftLoading(true)
+    try {
+      const res = await fetch(`/api/incidents/${incidentId}/ai/rca-draft`, { method: 'POST' })
+      if (!res.ok) return
+      const draft = await res.json() as {
+        five_why_steps: Array<{ why: string; answer: string }>
+        root_cause_summary: string
+        capa_suggestions: string[]
+      }
+      if (draft.five_why_steps?.length > 0) {
+        setMethod('five_why')
+        setFiveWhy(draft.five_why_steps)
+      }
+      if (draft.root_cause_summary) setRootCause(draft.root_cause_summary)
+      if (draft.capa_suggestions?.length > 0) {
+        setFindingsText(draft.capa_suggestions.map((s, i) => `${i + 1}. ${s}`).join('\n'))
+      }
+    } catch {
+      // Non-blocking — investigator can fill manually
+    } finally {
+      setAiDraftLoading(false)
+    }
+  }
+
   async function handleSubmit(e: React.FormEvent) {
     e.preventDefault()
     setSaving(true)
@@ -99,6 +125,16 @@ export function InvestigationForm({ incidentId, existingInvestigationId }: Props
 
   return (
     <form onSubmit={handleSubmit} className="space-y-6">
+      <div className="flex justify-end">
+        <button
+          type="button"
+          onClick={getAiDraft}
+          disabled={aiDraftLoading}
+          className="bg-purple-50 text-purple-700 border border-purple-300 rounded-lg px-3 py-1.5 text-xs font-semibold disabled:opacity-50 hover:bg-purple-100"
+        >
+          {aiDraftLoading ? 'Drafting…' : 'Get AI Draft'}
+        </button>
+      </div>
       <div>
         <label className="block text-sm font-medium text-gray-700 mb-1">RCA Method</label>
         <div className="flex gap-3">