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/workflow/templates/composables/useTemplateUrlLoader.ts

@@ -4,6 +4,7 @@ import { useRoute, useRouter } from 'vue-router'
 
 import { clearPreservedQuery } from '@/platform/navigation/preservedQueryManager'
 import { PRESERVED_QUERY_NAMESPACES } from '@/platform/navigation/preservedQueryNamespaces'
+import { useTelemetry } from '@/platform/telemetry'
 import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 
 import { useTemplateWorkflows } from './useTemplateWorkflows'
@@ -121,6 +122,7 @@ export function useTemplateUrlLoader() {
         })
       } else if (modeParam === 'linear') {
         // Set linear mode after successful template load
+        useTelemetry()?.trackEnterLinear({ source: 'template_url' })
         canvasStore.linearMode = true
       }
     } catch (error) {