ENG-1508: Open canvas as TldrawView immediately after creation (#892)

When a new canvas file is created, metadataCache.getFileCache() returns
null in the file-open handler because the cache hasn't indexed the new
file yet. This caused the file path to never be added to
pendingCanvasSwitches, so the active-leaf-change handler never switched
to TldrawView — leaving the user staring at raw JSON markdown.

Fix: directly call leaf.setViewState with VIEW_TYPE_TLDRAW_DG_PREVIEW
after openFile in createCanvas(), bypassing the event-based mechanism
for the creation case.

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

Author: trangdoan982

apps/obsidian/src/components/canvas/utils/tldraw.ts

@@ -14,6 +14,7 @@ import {
   TLDATA_DELIMITER_END,
   TLDATA_DELIMITER_START,
   TLDRAW_VERSION,
+  VIEW_TYPE_TLDRAW_DG_PREVIEW,
 } from "~/constants";
 import DiscourseGraphPlugin from "~/index";
 import { checkAndCreateFolder, getNewUniqueFilepath } from "~/utils/file";
@@ -178,8 +179,7 @@ export const createCanvas = async (plugin: DiscourseGraphPlugin) => {
   try {
     const filename = `Canvas-${format(new Date(), "yyyy-MM-dd-HHmm")}`;
     const folderpath = plugin.settings.canvasFolderPath;
-    const attachmentsFolder =
-      plugin.settings.canvasAttachmentsFolderPath;
+    const attachmentsFolder = plugin.settings.canvasAttachmentsFolderPath;
 
     await checkAndCreateFolder(folderpath, plugin.app.vault);
     await checkAndCreateFolder(attachmentsFolder, plugin.app.vault);
@@ -193,6 +193,10 @@ export const createCanvas = async (plugin: DiscourseGraphPlugin) => {
     const file = await plugin.app.vault.create(fname, content);
     const leaf = plugin.app.workspace.getLeaf(false);
     await leaf.openFile(file);
+    await leaf.setViewState({
+      type: VIEW_TYPE_TLDRAW_DG_PREVIEW,
+      state: { file: file.path },
+    });
 
     return file;
   } catch (e) {