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/content/cohesion-des-mondes/project.txt

@@ -0,0 +1,13 @@
+Title: Cohésion des mondes
+
+----
+
+Subtitle: Chroniques d'une cartographie sensible
+
+----
+
+Cover: - file://glu48yweigbs4wds
+
+----
+
+Uuid: eybhqikol6kaorby