Bump source to 0.9.2 and renumber the 0.x roadmap

- Set project.godot to 0.9.2 and add the matching changelog entry.
- Renumber the postponed work to 0.9.3 UI, 0.9.4 NPC, 0.9.5 textures and 0.9.6 integration, with 0.10.0 as the next minor release candidate.
- Remove the 1.0.0 milestone and post-1.0 planning; plan only 0.x patch/minor increments.
- Synchronize README, PLAN, architecture, status, memory and UI-copy version references.

docs/ui-copy.md

@@ -1,6 +1,6 @@
 # UI copy and button inventory
 
-Status: audit in progress for the 0.9.2 UI polish patch.
+Status: audit in progress for the 0.9.3 UI polish patch.
 
 ## Screen inventory