feat(rules): introduce block DSL, phase-based execution (#203)

* chore(deps): update submodule goutils

* docs(http): remove default client from README.md

* 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
- Default rules act as fallback handlers that execute only when no matching non-default rule exists in the pre phase
- IfElseBlockCommand now returns early when a condition matches with a nil Do block, instead of falling through to else blocks
- Add nil check for auth handler to allow requests when no auth is configured

* fix(rules): buffer log output before writing to stdout/stderr

* refactor(api/rules): remove IsResponseRule field from ParsedRule and related logic

* docs(rules): update examples to use block syntax

internal/route/rules/phase.go

@@ -0,0 +1,29 @@
+package rules
+
+import "strings"
+
+type PhaseFlag uint8
+
+const (
+	PhaseNone PhaseFlag = 0
+	PhasePre  PhaseFlag = 1 << (iota - 1)
+	PhasePost
+)
+
+func (phase PhaseFlag) IsPostRule() bool {
+	return phase&PhasePost != 0
+}
+
+func (phase PhaseFlag) String() string {
+	if phase == PhaseNone {
+		return "none"
+	}
+	var flags []string
+	if phase&PhasePre != 0 {
+		flags = append(flags, "PhasePre")
+	}
+	if phase&PhasePost != 0 {
+		flags = append(flags, "PhasePost")
+	}
+	return strings.Join(flags, ",")
+}