🧪 test: implement per-scenario state isolation and enhance validate-test-suite.sh

- Add pkg/bdd/steps/scenario_state.go with thread-safe per-scenario state manager
- Update auth_steps.go, jwt_retention_steps.go to use per-scenario state accessors
- Add LastSecret and LastError fields to ScenarioState for JWT retention testing
- Update steps.go with SetScenarioKeyForAllSteps function
- Update suite.go to generate scenario keys and clear state properly
- Mark config hot-reload scenarios as @flaky (timing-sensitive)
- Fix validate-test-suite.sh: add -p 1 flag for sequential execution, filter JSON logs, add --count flag
- Add CONFIG_SCHEMA.md documenting configuration architecture
- Split greet tests into v1/v2 sub-tests with explicit v2 enable/disable

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

features/greet/greet_test.go

@@ -1,16 +1,30 @@
 package greet
 
 import (
+	"os"
 	"testing"
 
 	"dance-lessons-coach/pkg/bdd/testsetup"
 )
 
 func TestGreetBDD(t *testing.T) {
-	config := testsetup.NewFeatureConfig("greet", "progress", false)
-	suite := testsetup.CreateTestSuite(t, config, "dance-lessons-coach BDD Tests - Greet Feature")
+	// Test suite with v2 disabled - run non-v2 scenarios only
+	t.Run("v1", func(t *testing.T) {
+		os.Setenv("GODOG_TAGS", "~@v2 && ~@skip")
+		config := testsetup.NewFeatureConfig("greet", "progress", false)
+		suite := testsetup.CreateTestSuite(t, config, "dance-lessons-coach BDD Tests - Greet Feature v1")
+		if suite.Run() != 0 {
+			t.Fatal("non-zero status returned, failed to run greet BDD tests with v2 disabled")
+		}
+	})
 
-	if suite.Run() != 0 {
-		t.Fatal("non-zero status returned, failed to run greet BDD tests")
-	}
+	// Test suite with v2 enabled - run v2 scenarios only
+	t.Run("v2", func(t *testing.T) {
+		os.Setenv("GODOG_TAGS", "@v2 && ~@skip")
+		config := testsetup.NewFeatureConfig("greet", "progress", false)
+		suite := testsetup.CreateTestSuite(t, config, "dance-lessons-coach BDD Tests - Greet Feature v2")
+		if suite.Run() != 0 {
+			t.Fatal("non-zero status returned, failed to run greet BDD tests with v2 enabled")
+		}
+	})
 }