docs: enrich docs/specs and remove placeholders

**Motivations:**
- Make docs/specs implementation-ready without empty sections or placeholders.

**Root causes:**
- Multiple specs still contained non-actionable placeholders (N/A, “see above”, "..."), and inconsistent “no cache” wording.

**Correctifs:**
- Replace placeholders with explicit tables, structures, and typed examples.
- Align “no cache / no memorization” statements where relevant.

**Evolutions:**
- Add a features doc entry to track the documentation enrichment effort.

**Pages affectées:**
- docs/specs/*
- docs/features/docs-specs-enrichment.md
- docs/leo.md
- docs/plan-enrich-docs-specs.md

docs/specs/billeterie.md

@@ -29,7 +29,7 @@ Bâtiment d'entrée du zoo. Point d'apparition et de départ des visiteurs.
     "current_queue_length": "integer"
   },
   "entry_log": [
-    { "timestamp": "...", "visitor_count": 5, "revenue": 50 }
+    { "timestamp": "timestamp", "visitor_count": 5, "revenue": 50 }
   ],
   "iso_x": "integer",
   "iso_y": "integer",