test(structure): split unit and integration suites; update tooling

- Move all existing tests under tests/Unit/ to prepare for dedicated integration tests.
- Add empty tests/Integration/ suite in phpunit.xml.
- Update phpunit.xml to define separate "unit" and "integration" test suites.
- composer.json:
  - Add `test` script (all tests) and `test:unit` for unit suite only.
- Makefile:
  - Update `test` target to run new composer test scripts.
  - Add `test-unit` target.

This allows running unit tests by default (make test / composer run test:unit)
while keeping integration tests isolated and triggered manually.

Author: bionicman

Makefile

@@ -9,4 +9,7 @@ lint:
 	composer run lint
 
 test:
-	composer run phpunit
+	composer run test
+
+test-unit:
+	composer run test:unit

composer.json

@@ -37,6 +37,7 @@
   ],
   "scripts": {
     "lint": "vendor/bin/phpcs --standard=phpcs.xml",
-    "phpunit": "vendor/bin/phpunit --testdox --colors=always --log-junit .phpunit.junit.xml"
+    "test": "vendor/bin/phpunit --testdox --colors=always --log-junit .phpunit.junit.xml",
+    "test:unit": "vendor/bin/phpunit --testsuite unit --testdox --colors=always --log-junit .phpunit.junit.xml"
   }
 }

phpunit.xml

@@ -3,8 +3,11 @@
          colors="true"
          verbose="true">
     <testsuites>
-        <testsuite name="Bblslug Test Suite">
-            <directory>tests</directory>
+        <testsuite name="unit">
+            <directory>tests/Unit</directory>
+        </testsuite>
+        <testsuite name="integration">
+            <directory>tests/Integration</directory>
         </testsuite>
     </testsuites>
 </phpunit>