Follow the GDScript style guide in every script

- Types on every parameter, return value and variable, and snake_case names
  (the player name limit is the constant MAX_NAME_LENGTH).
- Spelling fixes: *_triggered, character_selected, separator, caught_errors.
  The server's catched_errors key stays as the server sends it.
- Signals are connected with signal.connect() instead of by name.
- Code is ordered signals, constants, exported vars, vars, @onready vars,
  functions, with @onready on one line and two blank lines between functions.
- Every script starts with a ## description. Template comments, old LOC notes
  and commented-out code are gone, apart from the local play code.
- Lines are at most 100 characters, apart from the local play path.
- The screenshot tour turns off the blinking text cursor so pictures match.

tests/integration/test_players_panel.gd

@@ -105,7 +105,8 @@ func test_rows_follow_player_order_and_numbering() -> void:
 	_add("Marle")
 	_add("Lucca")
 
-	assert_array(_rows().map(func(row: PlayerRow) -> String: return row.player_object.player_name)) \
+	assert_array(_rows().map(
+			func(row: PlayerRow) -> String: return row.player_object.player_name)) \
 			.contains_exactly(["Crono", "Marle", "Lucca"])
 	assert_array(_rows().map(func(row: PlayerRow) -> int: return row.list_index)) \
 			.contains_exactly([0, 1, 2])