fix: align content field names with blueprints, fix API field calls

Content .txt files:
- narrative.txt (×4): Introduction → Intro
- chapter.txt (×3): Text → Body
- geoformat.txt: Intro → Text
- map.txt: move Text content into Intro field

narrative.json.php:
- parseChapter: $chapter->text() → $chapter->body()
- parseMarker: $marker->text() → $marker->body()
- parseMap: $map->text() → $map->intro()
- narrative root: $page->introduction() → $page->intro()

Also commits Kirby content directory rename (1_cohesion-des-mondes → cohesion-des-mondes)
and new _drafts content.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/site/blueprints/pages/chapter.yml

@@ -11,7 +11,7 @@ tabs:
             type: fields
             fields:
               blueprint: fields/blueprint
-              text:
+              body:
                 label: Contenu
                 type: blocks
                 fieldsets:

public/site/blueprints/pages/marker.yml

@@ -15,7 +15,7 @@ tabs:
                 label: Image de couverture
                 type: files
                 multiple: false
-              text:
+              body:
                 label: Contenu
                 type: blocks
                 fieldsets:

public/site/blueprints/pages/narrative.yml

@@ -22,7 +22,7 @@ tabs:
                 text: "{{ file.coverLabel }}"
                 multiple: false
                 width: 1/2
-              introduction:
+              intro:
                 label: Introduction
                 type: writer
           parts: