Refactor save manager validation and update state structure

- Updated the save manager to enforce a new format version (2) and improved validation checks for the save data structure.
- Enhanced the `validate_data` function to ensure all required fields are present and valid.
- Adjusted the handling of legacy saves and introduced new checks for various state fields.
- Improved number formatting in the global script for better readability of large numbers.
- Updated tests to reflect changes in the save manager and validation logic, ensuring compatibility with the new state structure.
- Added new tests for group indexing and production transactions to ensure correctness of entity management and resource production.

tests/test_stellar_rules.gd

@@ -84,7 +84,7 @@ func run() -> void:
     check(world.state.binds.RD.GG == 16.0 and world.state.binds.RD.AB == 120.0, "Planet multiplicity applied")
     check(world.state.amount.HP == 0.0 and world.state.stats.total_amount.HP == 1.0, "Created planets are bound, counted once")
     var saves: Node = root.get_node("SaveManager")
-    check(saves.validate_data({"state": world.state}) == "", "Planet carry save validates")
+    check(saves.validate_data({"format_version": 2, "app_version": "", "ui": {"current_page": 0}, "state": world.state}) == "", "Planet carry save validates")
     restored = fixture()
     restored.state = bytes_to_var(var_to_bytes(world.state))
     world._create_planets(world.state, "RD", 37.0, 0.0, 0.0, 0.7)
@@ -106,7 +106,7 @@ func run() -> void:
     check(world.state.amount.RP == 0.0 and world.state.amount["C1.3"] == 0.0, "Inherited planets never become free")
     world._evolve_batches(world.state, lifespan + width)
     check(world.state.binds.RD["C1.3"] == 0.0 and world.state.binds.TWD["C1.3"] == 4.0, "No planets left at extinct parent type")
-    check(saves.validate_data({"state": world.state}) == "", "Inherited state validates")
+    check(saves.validate_data({"format_version": 2, "app_version": "", "ui": {"current_page": 0}, "state": world.state}) == "", "Inherited state validates")
     dispose(world)
 
     world = fixture()
@@ -146,7 +146,7 @@ func run() -> void:
     check(world.state.amount.SN == 0.0 and world.state.amount.LNS == 1.0, "Supernova produces a remnant")
     check(world.state.amount.H == 8.0 and world.state.amount.He == 50.0 and world.state.amount.Met == 11.0, "Supernova returns table resources")
     check(not world.state.amount.has("blast"), "Supernova dispatches blast output")
-    check(saves.validate_data({"state": world.state}) == "", "Blast state validates")
+    check(saves.validate_data({"format_version": 2, "app_version": "", "ui": {"current_page": 0}, "state": world.state}) == "", "Blast state validates")
     dispose(world)
 
     world = fixture()