chore: add spec-kit and standardize signatures

- Added GitHub spec-kit for development workflow
- Standardized file signatures to Descomplicar® format
- Updated development configuration

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

care-booking-block/phpunit.xml.dist

@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+<phpunit
+    bootstrap="tests/bootstrap.php"
+    backupGlobals="false"
+    colors="true"
+    convertErrorsToExceptions="true"
+    convertNoticesToExceptions="true"
+    convertWarningsToExceptions="true"
+    testdox="true">
+    <testsuites>
+        <testsuite name="unit">
+            <directory prefix="test-" suffix=".php">./tests/unit/</directory>
+        </testsuite>
+        <testsuite name="integration">
+            <directory prefix="test-" suffix=".php">./tests/integration/</directory>
+        </testsuite>
+    </testsuites>
+    <logging>
+        <log type="coverage-html" target="build/coverage"/>
+        <log type="coverage-text" target="build/coverage.txt"/>
+        <log type="coverage-clover" target="build/logs/clover.xml"/>
+    </logging>
+    <filter>
+        <whitelist processUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">./includes</directory>
+            <file>./care-booking-block.php</file>
+        </whitelist>
+    </filter>
+</phpunit>