Align Go parser backends and PDF pipeline with Python (#16676)

Ports remaining Go parser wiring and PDF backends, adds tenant-aware VLM
dispatch, aligns post-processing with Python, and adds end-to-end
pipeline coverage with a generated six-page PDF.

internal/parser/parser/docx_parser_cgo_test.go

@@ -0,0 +1,64 @@
+//go:build cgo
+
+package parser
+
+import (
+	"archive/zip"
+	"bytes"
+	"testing"
+)
+
+func TestDOCXParser_ParseWithResult_CGOMinimalDocument(t *testing.T) {
+	p, err := NewDOCXParser(OfficeOxide)
+	if err != nil {
+		t.Fatalf("NewDOCXParser: %v", err)
+	}
+	data := minimalDOCX(t, "Hello from DOCX parser")
+	res := p.ParseWithResult("sample.docx", data)
+	if res.Err != nil {
+		t.Fatalf("ParseWithResult: %v", res.Err)
+	}
+	if got, want := res.OutputFormat, "markdown"; got != want {
+		t.Fatalf("OutputFormat = %q, want %q", got, want)
+	}
+	if res.Markdown == "" {
+		t.Fatal("Markdown is empty; want parsed content")
+	}
+}
+
+func minimalDOCX(t *testing.T, text string) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := zip.NewWriter(&buf)
+	writeZipFile(t, zw, "[Content_Types].xml", `<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
+  <Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+  <Default Extension="xml" ContentType="application/xml"/>
+  <Override PartName="/word/document.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml"/>
+</Types>`)
+	writeZipFile(t, zw, "_rels/.rels", `<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
+  <Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="word/document.xml"/>
+</Relationships>`)
+	writeZipFile(t, zw, "word/document.xml", `<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<w:document xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main">
+  <w:body>
+    <w:p><w:r><w:t>`+text+`</w:t></w:r></w:p>
+  </w:body>
+</w:document>`)
+	if err := zw.Close(); err != nil {
+		t.Fatalf("zip close: %v", err)
+	}
+	return buf.Bytes()
+}
+
+func writeZipFile(t *testing.T, zw *zip.Writer, name, body string) {
+	t.Helper()
+	w, err := zw.Create(name)
+	if err != nil {
+		t.Fatalf("create zip entry %s: %v", name, err)
+	}
+	if _, err := w.Write([]byte(body)); err != nil {
+		t.Fatalf("write zip entry %s: %v", name, err)
+	}
+}