Implement builtin chunk method as ingestion pipeline in GO (#16822)

### Summary

Implement builtin chunk mehtod as ingestion pipeline in GO

internal/parser/parser/audio_parser.go

@@ -0,0 +1,97 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+// AudioParser validates and stores configuration for audio files.
+// The actual speech-to-text transcription is performed by the
+// component-layer maybeDispatchAudio, which mirrors Python's
+// Parser._audio() in rag/flow/parser/parser.py.
+
+package parser
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+)
+
+// audioExtensions mirrors Python's ParserParam.Defaults() audio suffix
+// list: ["da","wave","wav","mp3","aac","flac","ogg","aiff","au","midi",
+// "wma","realaudio","vqf","oggvorbis","ape"].
+var audioExtensions = map[string]bool{
+	"da": true, "wave": true, "wav": true, "mp3": true,
+	"aac": true, "flac": true, "ogg": true, "aiff": true,
+	"au": true, "midi": true, "wma": true, "realaudio": true,
+	"vqf": true, "oggvorbis": true, "ape": true,
+}
+
+// AudioParser handles audio files for transcription. The struct mirrors
+// the configuration from setups["audio"]:output_format and
+// setups["audio"].vlm.llm_id.
+type AudioParser struct {
+	VLMModelID   string // vlm.llm_id — identifies the speech-to-text model
+	OutputFormat string
+}
+
+// NewAudioParser constructs an AudioParser.
+func NewAudioParser() *AudioParser {
+	return &AudioParser{}
+}
+
+// ConfigureFromSetup reads audio-specific configuration from the
+// parser setup map. It extracts vlm.llm_id and output_format.
+func (p *AudioParser) ConfigureFromSetup(setup map[string]any) {
+	if p == nil || setup == nil {
+		return
+	}
+	if vlm, ok := setup["vlm"].(map[string]any); ok {
+		if llmID, ok := vlm["llm_id"].(string); ok && llmID != "" {
+			p.VLMModelID = llmID
+		}
+	}
+	if v, ok := setup["output_format"].(string); ok && v != "" {
+		p.OutputFormat = v
+	}
+}
+
+// ParseWithResult implements ParseResultProducer. It validates the
+// file extension against the audio extension whitelist. The actual
+// speech-to-text transcription happens via maybeDispatchAudio at the
+// component layer (mirrors Python's LLMBundle.transcription call).
+func (p *AudioParser) ParseWithResult(filename string, data []byte) ParseResult {
+	ext := strings.ToLower(filepath.Ext(filename))
+	if len(ext) > 1 && ext[0] == '.' {
+		ext = ext[1:]
+	}
+	if ext == "" || !audioExtensions[ext] {
+		return ParseResult{
+			Err: fmt.Errorf("audio: unsupported extension %q (filename: %s); accepted: .da/.wav/.wave/.mp3/.aac/.flac/.ogg/.aiff/.au/.midi/.wma/.realaudio/.vqf/.oggvorbis/.ape", ext, filename),
+		}
+	}
+
+	// OutputFormat and VLMModelID are consumed by maybeDispatchAudio.
+	outFmt := p.OutputFormat
+	if outFmt == "" {
+		outFmt = "text"
+	}
+
+	return ParseResult{
+		OutputFormat: outFmt,
+		File: map[string]any{
+			"name": filename,
+			"size": len(data),
+		},
+	}
+}