Add multilingual Agila learning examples and Git practice guide

en/ada-contracts-and-review/README.md

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+# A reviewed progress component
+
+Extend the level component with a clearly specified operation of your own. Submit both successful and expected-failure evidence plus a reviewable explanation.
+
+- Record the allowed inputs and promised result.
+- Keep assertion checking enabled and record compiler settings.
+- Test low and high valid inputs and one precondition violation separately.
+- Demonstrate that a deliberately wrong body is caught, then restore it.
+- Explain a remaining limitation and identify one next learning step.

en/ada-contracts-and-review/main.adb

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+pragma Assertion_Policy (Check);
+with Ada.Text_IO;
+
+procedure Main is
+   subtype Level is Integer range 0 .. 10;
+   function Next_Level (Current : Level) return Level
+     with Pre => Current < Level'Last,
+          Post => Next_Level'Result = Current + 1;
+
+   function Next_Level (Current : Level) return Level is
+   begin
+      return Current + 1;
+   end Next_Level;
+begin
+   pragma Assert (Next_Level (0) = 1);
+   pragma Assert (Next_Level (9) = 10);
+   Ada.Text_IO.Put_Line ("Two boundary checks passed");
+end Main;