Implement gradual evolution mechanics and simulation time handling in Owniverse.GI

- Added `blastability` property to entities for vulnerability tracking.
- Enhanced planet string parsing with validation and error handling.
- Introduced `simulation_rules.md` to document evolution mechanics and rules.
- Created tests for time progression and stellar evolution rules, ensuring correct handling of fractional years and resource production.
- Implemented `simulation_time.gd` for managing accumulated time and year processing.
- Updated tests to validate legacy save compatibility and migration to new time schema.

stage/stage.gd

@@ -80,7 +80,7 @@ var locked_items: Array = []
 
 
 func set_datetime(value: float):
-    date_time.text = str(snapped(value, 0.1))
+    date_time.text = Global.format_number(value, 5) if value != 0.0 else "0.0"
 
 #region Item manipulations: update and visibility
 
@@ -380,6 +380,7 @@ func load_data() -> bool:
     complete.merge(restored, true)
     owniverse.state = complete
     owniverse.new_state = complete
+    owniverse.migrate_time_precision()
     owniverse.refresh_item_amounts()
     pending_page = clampi(int(game_data.get("ui", {}).get("current_page", 0)), 0, PAGE_COUNT - 1)
     _restore_page.call_deferred()