docs(excalidraw,roadmap): #78 H1-H3 doc utilisateur + #61/#74 optionnels non retenus

- README FR/EN : .excalidraw dans les formats supportes + section Diagrammes Excalidraw
- Guide integre : nouvelle section Excalidraw (i18n FR/EN) + note compatibilite plugin Obsidian
- ROADMAP : #78 termine (B5/F3/H1-H3), C8/F2 non retenus ; #61 et #74 optionnels marques non retenus
- CHANGELOG : entree Documentation

README.md

@@ -58,6 +58,7 @@
 - **🏷️ Tag Cloud** : Filtering by tags extracted from YAML frontmatters
 - **🔗 Wikilinks** : `[[internal links]]` from Obsidian are clickable
 - **🖼️ Obsidian Images** : Full support for all Obsidian image syntaxes with intelligent resolution
+- **🎨 Excalidraw Diagrams** : Native viewer/editor for `.excalidraw` and `.excalidraw.md` files (sandboxed iframe, autosave, dark/light theme, diagram text indexed for search)
 - **🎨 Syntax Highlight** : Syntax highlighting for code blocks
 - **🌓 Light/Dark Theme** : Toggle persisted in localStorage
 - **📡 Real-time Sync** : Automatic file monitoring via watchdog with incremental index updates
@@ -740,7 +741,7 @@ curl "http://localhost:2020/api/file/Recipes?path=pizza.md"
 | `ext:<type>` | Filter by file type | `ext:md kubernetes` |
 | `"exact phrase"` | Phrase search | `tag:"multiple words"` |
 
-Extension filter examples: `ext:sh` for bash scripts, `ext:py` for Python scripts, `ext:md` for Markdown files, `ext:pdf` for PDF documents (text-extracted content is indexed).
+Extension filter examples: `ext:sh` for bash scripts, `ext:py` for Python scripts, `ext:md` for Markdown files, `ext:pdf` for PDF documents, `ext:excalidraw` for Excalidraw diagrams (text-extracted content is indexed).
 
 ### PDF support
 
@@ -752,6 +753,13 @@ PDF metadata (pages, title, author) is available via `GET /api/file/{vault}/pdf/
 
 **Limitations:** no OCR (scanned PDFs aren't searchable), no annotation, no editing of the PDF itself.
 
+### Excalidraw diagrams
+
+`.excalidraw` and `.excalidraw.md` files open in a full visual Excalidraw editor embedded in a sandboxed iframe — draw, edit and save without leaving ObsiGate.
+Changes are saved automatically (2s debounce) or with `Ctrl+S`; the editor follows the light/dark theme.
+Text labels inside the diagram elements are extracted on indexing, so diagram content is searchable via the full-text search (`ext:excalidraw`).
+Files created with the **Obsidian Excalidraw plugin** (including the compressed `.excalidraw.md` format) are compatible.
+
 Operators are combinable: `tag:linux vault:IT ext:md server web` searches for "server web" in Markdown files of the IT vault with the linux tag.
 
 ### Keyboard Shortcuts