fix: honor parser params and image VLM system_prompt in Go ingestion (#17334)

## Summary
Fix the Go ingestion pipeline so that several parser setup switches and
the
image VLM prompt are actually honored end-to-end (previously the DSL
fields
existed but the Go code never read them).

- **DOCX** (`docx_parser.go`, `docx_postprocess.go`): read `remove_toc`
and
  `remove_header_footer`; apply to both JSON and markdown output paths
  (outline-based TOC removal with a text-heuristic fallback, plus
  header/footer section filtering).
- **HTML** (`html_parser.go`, `html_postprocess.go`, `text_toc.go`):
read
`remove_header_footer` (pre-parse strip of `<header>`/`<footer>` and
ARIA
`banner`/`contentinfo`) and `remove_toc` (post-parse
`remove_contents_table`
  heuristic).
- **Markdown** (`markdown_parser.go`): read `flatten_media_to_text` and
force
  media blocks to text when enabled.
- **Image VLM** (`media_dispatch.go`): read `system_prompt` instead of
`prompt`
  so the user-configured image VLM prompt is no longer silently dropped
  (`prompt` remains the video family key).

All flags are wired through `ConfigureFromSetup`, which the dispatch
layer
already invokes for every family, so the behavior is live rather than
dead code.

## Test plan
- New unit tests: `docx_postprocess_test.go`, `html_parser_test.go`,
`text_toc_test.go`, `markdown_parser_test.go`, `media_dispatch_test.go`.
- `bash build.sh --test ./internal/parser/parser/...
./internal/ingestion/component/...`

## Notes
- The `File` component is excluded from this migration scope.
- Relates to the Python→Go parity diff (Parser 1.8–1.11, 1.15).

internal/parser/parser/html_parser.go

@@ -25,7 +25,10 @@ import (
 	"golang.org/x/net/html"
 )
 
-type HTMLParser struct{}
+type HTMLParser struct {
+	RemoveHeaderFooter bool
+	RemoveTOC          bool
+}
 
 func NewHTMLParser() *HTMLParser {
 	return &HTMLParser{}
@@ -35,6 +38,21 @@ func (p *HTMLParser) String() string {
 	return "HTMLParser"
 }
 
+// ConfigureFromSetup reads the HTML family setup map. Mirrors the
+// Python parser.py HTML setup keys: remove_header_footer (pre-parse
+// tag strip) and remove_toc (post-parse text heuristic).
+func (p *HTMLParser) ConfigureFromSetup(setup map[string]any) {
+	if p == nil || setup == nil {
+		return
+	}
+	if v, ok := setup["remove_header_footer"].(bool); ok {
+		p.RemoveHeaderFooter = v
+	}
+	if v, ok := setup["remove_toc"].(bool); ok {
+		p.RemoveTOC = v
+	}
+}
+
 // ParseWithResult emits one item per block-level HTML element
 // (headings, paragraphs, lists, pre blocks). The walker is a
 // pure-Go replacement for the previous `fmt.Printf` debug output:
@@ -49,12 +67,27 @@ func (p *HTMLParser) String() string {
 // separate ck_type — the python HtmlParser collapses inline
 // formatting into the parent block's text.
 func (p *HTMLParser) ParseWithResult(ctx context.Context, filename string, data []byte) ParseResult {
+	// remove_header_footer: pre-parse strip of <header>/<footer> tags
+	// and ARIA role=banner/contentinfo elements (mirrors Python
+	// parser.py:1083-1084 remove_header_footer_html_blob).
+	if p.RemoveHeaderFooter {
+		cleaned, err := stripHTMLHeaderFooter(data)
+		if err != nil {
+			return ParseResult{Err: fmt.Errorf("html remove_header_footer: %w", err)}
+		}
+		data = cleaned
+	}
 	doc, err := html.Parse(bytes.NewReader(data))
 	if err != nil {
 		return ParseResult{Err: fmt.Errorf("html parse: %w", err)}
 	}
 	var items []map[string]any
 	walkHTMLBlocks(doc, &items)
+	// remove_toc: post-parse text heuristic (mirrors Python
+	// parser.py:1087-1088 remove_toc → remove_contents_table).
+	if p.RemoveTOC {
+		items = removeContentsTable(items, false)
+	}
 	if items == nil {
 		items = []map[string]any{{"text": "", "doc_type_kwd": "text"}}
 	}