refactor(rules): introduce block DSL, phase-based execution, and flow validation

- add block syntax parser/scanner with nested @blocks and elif/else support
- restructure rule execution into explicit pre/post phases with phase flags
- classify commands by phase and termination behavior
- enforce flow semantics (default rule handling, dead-rule detection)
- expand HTTP flow coverage with block + YAML parity tests and benches
- refresh rules README/spec and update playground/docs integration

internal/api/v1/route/playground.go

@@ -298,7 +298,7 @@ func parseRules(rawRules []RawRule) ([]ParsedRule, rules.Rules, error) {
 			On:              onStr,
 			Do:              doStr,
 			ValidationError: validationErr,
-			IsResponseRule:  rule.IsResponseRule(),
+			// IsResponseRule:  rule.Requirement()&rules.RequirementFlagResponse != 0,
 		})
 
 		// Only add valid rules to execution list