feat: show investigation panel on incident detail page

Fetches investigation record (5-Why steps, findings, root cause,
alcohol test, witness refs) and renders below incident details.
Shows completion status and investigator name.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CPf5Rc8QPx6V8KLEEgfKEQ

app/(protected)/hse/incidents/[id]/page.tsx

@@ -6,6 +6,7 @@ import { IncidentDetail, type Incident } from '@/components/incidents/incident-d
 import { IncidentHeader } from '@/components/incidents/incident-header'
 import { SimilarIncidentsPanel } from '@/components/incidents/similar-incidents-panel'
 import { ClosurePanel } from '@/components/incidents/closure-panel'
+import { InvestigationPanel } from '@/components/incidents/investigation-panel'
 
 interface Props {
   params: Promise<{ id: string }>
@@ -35,6 +36,17 @@ export default async function HseIncidentDetailPage({ params }: Props) {
 
   const status = (incident as { status: string }).status
 
+  const { data: investigation } = await supabase
+    .from('investigations')
+    .select(`
+      id, method, five_why_steps, fishbone_categories,
+      findings_text, root_cause_summary, alcohol_test_result,
+      witness_statement_refs, completed_at,
+      investigator:users!investigator_id (name, email)
+    `)
+    .eq('incident_id', id)
+    .maybeSingle()
+
   const needsJkkp = Boolean(
     (incident as { is_fatality?: boolean }).is_fatality ||
     (incident as { is_serious_bodily_injury?: boolean }).is_serious_bodily_injury ||
@@ -56,6 +68,10 @@ export default async function HseIncidentDetailPage({ params }: Props) {
       <main className="max-w-3xl mx-auto px-4 py-6">
         <IncidentDetail incident={incident as unknown as Incident} />
 
+        {investigation && (
+          <InvestigationPanel investigation={investigation as never} />
+        )}
+
         {needsJkkp && (
           <div className="mt-4 flex gap-3 flex-wrap">
             <a