feat: track app mode entry and shared workflow loading (#9720)

## Summary

- Track entering app mode from template URL (`source: template_url`) and
default view dialog (`source: default_view_dialog`)
- Tag shared workflow loads with `openSource: 'shared'` instead of
defaulting to `'unknown'`
- Rename telemetry event from `app:toggle_linear_mode` to
`app:app_mode_opened`

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9720-feat-track-app-mode-entry-and-shared-workflow-loading-31f6d73d365081af8c6ae3247a50cf3f)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/platform/telemetry/TelemetryRegistry.ts

@@ -4,6 +4,7 @@ import type {
   AuthMetadata,
   BeginCheckoutMetadata,
   EnterLinearMetadata,
+  ShareFlowMetadata,
   ExecutionErrorMetadata,
   ExecutionSuccessMetadata,
   ExecutionTriggerSource,
@@ -160,6 +161,10 @@ export class TelemetryRegistry implements TelemetryDispatcher {
     this.dispatch((provider) => provider.trackEnterLinear?.(metadata))
   }
 
+  trackShareFlow(metadata: ShareFlowMetadata): void {
+    this.dispatch((provider) => provider.trackShareFlow?.(metadata))
+  }
+
   trackPageVisibilityChanged(metadata: PageVisibilityMetadata): void {
     this.dispatch((provider) => provider.trackPageVisibilityChanged?.(metadata))
   }