feat: send missing node data to ClickHouse (#10132)

## Summary
- When users open/import a workflow with missing nodes, we already track
this via Mixpanel
- This adds a parallel fire-and-forget POST to
`/api/internal/cloud_analytics` so the data also lands in **ClickHouse**
as `frontend:missing_nodes_detected` events
- Payload includes `missing_class_types[]`, `missing_count`, and
`source` (file_button/file_drop/template/unknown)

## Motivation
The frontend is where the **high-value** missing node signal lives —
most users see "missing nodes" and never submit. The backend only
catches the rare case where someone submits anyway. This change captures
both sides.

Companion cloud PR: https://github.com/Comfy-Org/cloud/pull/2886

## Changes
- `MixpanelTelemetryProvider.ts`: Added
`reportMissingNodesToClickHouse()` private method, called from
`trackWorkflowImported()` and `trackWorkflowOpened()`
- Only fires when `missing_node_count > 0`
- Fire-and-forget (`.catch(() => {})`) — no impact on user experience
- Uses existing `api.fetchApi()` which handles auth automatically

## Test plan
- [ ] Open a workflow with missing nodes → verify
`frontend:missing_nodes_detected` event appears in ClickHouse
- [ ] Open a workflow with no missing nodes → verify no event is sent
(check network tab)
- [ ] Verify Mixpanel tracking still works as before

🤖 Generated with [Claude Code](https://claude.com/claude-code)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10132-feat-send-missing-node-data-to-ClickHouse-3266d73d365081559db5ed3efde33e95)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: GitHub Action <action@github.com>

src/platform/telemetry/initTelemetry.ts

@@ -25,13 +25,15 @@ export async function initTelemetry(): Promise<void> {
       { MixpanelTelemetryProvider },
       { GtmTelemetryProvider },
       { ImpactTelemetryProvider },
-      { PostHogTelemetryProvider }
+      { PostHogTelemetryProvider },
+      { ClickHouseTelemetryProvider }
     ] = await Promise.all([
       import('./TelemetryRegistry'),
       import('./providers/cloud/MixpanelTelemetryProvider'),
       import('./providers/cloud/GtmTelemetryProvider'),
       import('./providers/cloud/ImpactTelemetryProvider'),
-      import('./providers/cloud/PostHogTelemetryProvider')
+      import('./providers/cloud/PostHogTelemetryProvider'),
+      import('./providers/cloud/ClickHouseTelemetryProvider')
     ])
 
     const registry = new TelemetryRegistry()
@@ -39,6 +41,7 @@ export async function initTelemetry(): Promise<void> {
     registry.registerProvider(new GtmTelemetryProvider())
     registry.registerProvider(new ImpactTelemetryProvider())
     registry.registerProvider(new PostHogTelemetryProvider())
+    registry.registerProvider(new ClickHouseTelemetryProvider())
 
     setTelemetryRegistry(registry)
   })()

src/platform/telemetry/providers/cloud/ClickHouseTelemetryProvider.ts

@@ -0,0 +1,45 @@
+import { api } from '@/scripts/api'
+
+import type { TelemetryProvider, WorkflowImportMetadata } from '../../types'
+
+/**
+ * ClickHouse Telemetry Provider - Cloud Build Implementation
+ *
+ * Sends observability events to the cloud backend's ClickHouse pipeline
+ * via POST /api/internal/cloud_analytics. Currently tracks missing node
+ * data when users open/import workflows with unsupported nodes.
+ *
+ * This provider is separate from Mixpanel because ClickHouse is the
+ * canonical store for post-hoc analytics (per observability philosophy).
+ *
+ * CRITICAL: OSS Build Safety
+ * This file is tree-shaken away in OSS builds (DISTRIBUTION unset).
+ */
+export class ClickHouseTelemetryProvider implements TelemetryProvider {
+  trackWorkflowImported(metadata: WorkflowImportMetadata): void {
+    this.reportMissingNodes(metadata)
+  }
+
+  trackWorkflowOpened(metadata: WorkflowImportMetadata): void {
+    this.reportMissingNodes(metadata)
+  }
+
+  private reportMissingNodes(metadata: WorkflowImportMetadata): void {
+    if (metadata.missing_node_count <= 0) return
+
+    api
+      .fetchApi('/internal/cloud_analytics', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          event_name: 'node_missing',
+          event_data: {
+            missing_class_types: metadata.missing_node_types,
+            missing_count: metadata.missing_node_count,
+            source: metadata.open_source ?? 'unknown'
+          }
+        })
+      })
+      .catch(() => {})
+  }
+}