feat(phase6a-v1.2): dual-mode custom-event enrichment (v1.0 + v2.0 aliases)

- Prisma: posthog_person_cache (24h TTL), posthog_group_cache, session_custom_events
- SessionMeta: +posthogDistinctId, +groupKey, +customEventCount
- PostHog client: listSessionEvents, getPerson, getGroup
- posthog-cache.ts: cache-with-stale-refresh for person + group properties
- event-taxonomy.ts: dual-mode alias map (vin_decoded↔vin_decode_initiated,
  vin_decode_success↔vin_decode_succeeded, vin_decode_error↔vin_decode_failed,
  payment_success↔payment_succeeded). 56 tracked event names total.
- enrich.ts: per-session custom events fetch, persist to session_custom_events,
  attach user_properties + group_properties via cache.
- tagger.ts: 14 new custom-event tags
  (vin_decode_fail_pattern, provider_reliability_issue, payment_friction,
   payment_ui_silent_failure (P0), payment_failed_session, checkout_abandonment,
   downgrade_pending, compatibility_quality_gap, parts_export_abandoned,
   search_validation_friction, onboarding_stuck, upgrade_hesitation,
   power_user_path, at_risk_active_session, provider_mismatch,
   api_key_friction, webhook_setup_struggle); group-context priority bump.
- heuristic.ts: customEventPromoteReasons() — 10 custom-event promote signals.
- compress.ts: merge_rrweb_and_custom_events interleaving with ⤷ EVENT: prefix,
  ±1.5s grouping, standalone flush for events with no nearby rrweb. Adds
  company_context header line; key_events lists top-5 custom event counts.
- /insights page: +Events column. /insights/sessions/[id]: collapsible custom
  events table + group key display.

Graceful: when Sase.tr emits 0 custom events the pipeline falls back to
rrweb-only tagging from Phase 6a v1.1.

PRD: behavioral-insight-pipeline-prd-1.md (v1.2),
     sase-posthog-events-prd.md (Sase.tr-side, separate codebase).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/prisma/schema.prisma

@@ -117,8 +117,10 @@ model SessionMeta {
   id                String   @id
   projectKey        String
   userIdHash        String?
+  posthogDistinctId String?
   isAuthenticated   Boolean  @default(false)
   subscriptionTier  String?
+  groupKey          String?
   startedAt         DateTime
   durationMs        Int
   pageviewCount     Int      @default(0)
@@ -133,6 +135,7 @@ model SessionMeta {
   tags              String[]
   severity          String?
   score             Int?
+  customEventCount  Int      @default(0)
   rawMetadataUrl    String?
   status            String   @default("pending_signal")
   fingerprint       String?
@@ -176,3 +179,41 @@ model IngestionWatermark {
 
   @@map("ingestion_watermarks")
 }
+
+// PostHog identify() person properties cache (24h TTL).
+model PosthogPersonCache {
+  distinctId   String   @id
+  properties   Json
+  groups       Json?
+  refreshedAt  DateTime
+  ttlAt        DateTime
+
+  @@index([ttlAt])
+  @@map("posthog_person_cache")
+}
+
+// PostHog group analytics (e.g. company) cache (24h TTL).
+model PosthogGroupCache {
+  groupType    String
+  groupKey     String
+  properties   Json
+  refreshedAt  DateTime
+  ttlAt        DateTime
+
+  @@id([groupType, groupKey])
+  @@index([ttlAt])
+  @@map("posthog_group_cache")
+}
+
+// Per-session custom events fetched from PostHog (joined by $session_id).
+// Stored so compression can interleave them with rrweb timeline.
+model SessionCustomEvent {
+  id          BigInt   @id @default(autoincrement())
+  sessionId   String
+  eventName   String
+  timestamp   DateTime
+  properties  Json
+
+  @@index([sessionId, timestamp])
+  @@map("session_custom_events")
+}

apps/web/src/app/insights/page.tsx

@@ -66,13 +66,14 @@ export default async function InsightsPage() {
               <TableHead>Tags</TableHead>
               <TableHead>Started</TableHead>
               <TableHead>Duration</TableHead>
+              <TableHead>Events</TableHead>
               <TableHead>URL</TableHead>
             </TableRow>
           </TableHeader>
           <TableBody>
             {recent.length === 0 ? (
               <TableRow>
-                <TableCell colSpan={8} className="text-center text-xs text-muted-foreground">
+                <TableCell colSpan={9} className="text-center text-xs text-muted-foreground">
                   No tagged sessions yet — pipeline may still be warming up.
                 </TableCell>
               </TableRow>
@@ -100,6 +101,7 @@ export default async function InsightsPage() {
                     {s.startedAt.toISOString().slice(0, 19).replace("T", " ")}
                   </TableCell>
                   <TableCell className="text-xs">{Math.round(s.durationMs / 1000)}s</TableCell>
+                  <TableCell className="text-xs font-mono">{s.customEventCount || "—"}</TableCell>
                   <TableCell className="max-w-[200px] truncate font-mono text-xs">
                     {s.startUrl ?? "—"}
                   </TableCell>

apps/web/src/app/insights/sessions/[id]/page.tsx

@@ -42,6 +42,12 @@ export default async function SessionDetailPage({
   });
   if (!s) notFound();
 
+  const customEvents = await prisma.sessionCustomEvent.findMany({
+    where: { sessionId: id },
+    orderBy: { timestamp: "asc" },
+    take: 100,
+  });
+
   const bucket = process.env.INSIGHT_COMPRESSED_BUCKET ?? "insight-compressed";
   const timeline = s.compressed
     ? await fetchTimeline(bucket, s.compressed.semanticTimelineMinioKey)
@@ -84,6 +90,35 @@ export default async function SessionDetailPage({
         </div>
       )}
 
+      {customEvents.length > 0 && (
+        <details className="rounded-md border bg-muted/20 p-3 text-xs">
+          <summary className="cursor-pointer font-medium">
+            Custom events ({customEvents.length})
+          </summary>
+          <table className="mt-2 w-full font-mono">
+            <tbody>
+              {customEvents.map((e) => (
+                <tr key={String(e.id)} className="border-t">
+                  <td className="py-1 pr-3 text-muted-foreground">
+                    {e.timestamp.toISOString().slice(11, 19)}
+                  </td>
+                  <td className="py-1 pr-3">{e.eventName}</td>
+                  <td className="py-1 truncate max-w-[600px]">
+                    {JSON.stringify(e.properties).slice(0, 200)}
+                  </td>
+                </tr>
+              ))}
+            </tbody>
+          </table>
+        </details>
+      )}
+
+      {s.groupKey && (
+        <div className="text-xs text-muted-foreground">
+          company group: <span className="font-mono">{s.groupKey}</span>
+        </div>
+      )}
+
       <h3 className="mt-4 text-sm font-medium">Semantic Timeline</h3>
       <pre className="rounded-md border bg-muted/30 p-3 text-xs whitespace-pre-wrap font-mono">
         {timeline ?? "(no compressed timeline yet)"}