Modernized build tooling

docs/behaviour.md

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+# Behaviour Specifications
+
+All features are documented as Gherkin scenarios that serve as both tests and documentation.
+
+## CLI Features
+
+### Default Greeting
+
+```gherkin
+Scenario: Default greeting
+  When I run "python -m boilerplate"
+  Then the exit code should be 0
+  And the output should contain "Hello, World!"
+```
+
+### Custom Name Greeting
+
+```gherkin
+Scenario: Custom name greeting
+  When I run "python -m boilerplate --name Alice"
+  Then the exit code should be 0
+  And the output should contain "Hello, Alice!"
+```
+
+### Multiple Greetings
+
+```gherkin
+Scenario: Multiple greetings
+  When I run "python -m boilerplate --count 3"
+  Then the exit code should be 0
+  And the output should contain "Hello, World!" 3 times
+```
+
+## Fuzz Testing
+
+We use Hypothesis to ensure our CLI handles edge cases:
+
+```gherkin
+@hypothesis
+Scenario: Fuzz test greeting names
+  When I fuzz test the CLI with random names
+  Then all invocations should succeed
+```
+
+This runs 1000+ test cases with randomly generated inputs including:
+- Empty strings
+- Unicode characters
+- Emojis
+- Very long strings
+- Special characters