fix(search,excalidraw,e2e): recherche cassee + corruption .excalidraw.md + tests E2E #78

- frontend/js/search.js : onSearchFilter appelee avec (vault, query, results) — renvoyait undefined, cassait le rendu et basculait sur la recherche offline (0 resultat). Regression plugins depuis 30f2df3.
- frontend/excalidraw-editor.html + js/excalidraw-viewer.js : ignorer onChange au montage (plus d'auto-save spurieux qui reecrivait .excalidraw.md en JSON brut) + preservation du format Obsidian frontmatter + compressed-json a la sauvegarde.
- frontend/js/app.js : __OBSIGATE_BOOTED pose apres init() (splash + E2E attendent les handlers lies).
- tests/e2e : goHome/login attendent le boot ; excalidraw.spec.js reecrit avec les selecteurs reels (modal, context menu, canvas.first()).
- ROADMAP : C8 (creation via menu contextuel) marque fait.
- Verifie : 86/86 E2E chromium-desktop, 599 backend, ruff, validate-imports, JSDOM.

frontend/js/excalidraw-viewer.js

@@ -114,11 +114,22 @@ export function renderExcalidraw(container, data, vaultName, filePath, opts = {}
  */
 async function _saveExcalidrawFile(state, excalidrawData) {
   try {
-    const jsonStr = JSON.stringify(excalidrawData, null, 2);
+    const isMd = (state.path || '').toLowerCase().endsWith('.excalidraw.md');
+    let content;
+    if (isMd && excalidrawData && excalidrawData.compressed) {
+      // Preserve the Obsidian Excalidraw plugin format: frontmatter +
+      // compressed-json block. Writing raw JSON here would destroy the
+      // .excalidraw.md file (the plugin would no longer recognize it).
+      content = `---\nexcalidraw-plugin: parsed\n---\n\n\`\`\`compressed-json\n${excalidrawData.compressed}\n\`\`\`\n`;
+    } else {
+      // Transport-only field must not leak into the pure JSON format.
+      const { compressed, ...scene } = excalidrawData || {};
+      content = JSON.stringify(scene, null, 2);
+    }
     await api(`/api/file/${encodeURIComponent(state.vault)}/save?path=${encodeURIComponent(state.path)}&backup=false`, {
       method: 'PUT',
       headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ content: jsonStr }),
+      body: JSON.stringify({ content }),
     });
     // Toast is handled by the caller or we show a quick one
     showToast('Excalidraw saved', 'success');