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/io.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/yusing/godoxy/internal/common"
 	"github.com/yusing/godoxy/internal/logging/accesslog"
+	gperr "github.com/yusing/goutils/errs"
 )
 
 type noopWriteCloser struct {
@@ -30,7 +31,7 @@ var (
 	testFilesLock sync.Mutex
 )
 
-func openFile(path string) (io.WriteCloser, error) {
+func openFile(path string) (io.WriteCloser, gperr.Error) {
 	switch path {
 	case "/dev/stdout":
 		return stdout, nil