Feat(ingestion): align image to MinIO upload, unify chunk-id computation and add PPT parsing support (#17111)

## Summary

Align the Go ingestion pipeline with Python's `image` → `img_id`
persistence semantics, and unify the chunk-id computation across all
paths.

### Changes

**1. Image upload at chunker stage **

- Add `ImageUploader` type and `DefaultImageUploader` in
`internal/ingestion/component/image_uploader.go` — the write-side
counterpart to `FetchBinary`, storing raw image bytes at `(bucket=kbID,
key=chunkID)`, no re-encoding.
- Add `uploadOneImage` — pure upload primitive (bytes in, `img_id` out),
does not touch chunk maps.
- Add `uploadChunkImages` / `uploadChunkImage` — caller-side helper:
decodes `image` from a chunk, uploads bytes, writes `ck["img_id"]`,
`delete(ck,"image")` , bounded by a process-wide semaphore (default 10,
env `MAX_CONCURRENT_MINIO`).
- Wire via `imageUploadDecorator` in `register.go`: every chunker runs
the upload pass at invocation time, writing `ck["id"]` before upload and
dropping image bytes right after — peak memory = single chunk image
lifetime.

**2. Unify chunk-id computation**

- Consolidate three separate id-computation paths (`component.ChunkID`,
`task.ChunkID`, inline `FormatUint` in API) into one:
`common.ChunkID(docID, text string)`, using `%016x` +
`xxhash.Sum64String(text+docID)` (matching Python `hexdigest()`).
- The chunker decorator writes `ck["id"]` via `common.ChunkID`; the
persist stage (`ProcessChunksForPipeline`) falls back to the same
function (`if !exists id`).
- The API AddChunk path now also calls `common.ChunkID` instead of the
divergent `FormatUint(xxhash.Sum64(...))` — fixing a pre-existing
inconsistency.
- Delete `internal/ingestion/component/chunk_id.go` and
`internal/ingestion/task/chunk_builder.go` (both were pure forwarding
shells).

**3. Preserve `img_id` (never deleted)**

- `img_id` is a persistent index field (Infinity, OB) and the only
consumer-side reference for image retrieval; it is NEVER removed from
the chunk map. Only `image` (raw data URL) is dropped after upload.

**4. PPT parser support**
Previously PPT parsing failed. Add support to parse.

### Key design decisions

| Decision | Choice |
|----------|--------|
| Upload timing | Chunker stage (not persist), so image bytes are
dropped immediately — bounds peak memory to one chunk image |
| Upload concurrency | Process-wide semaphore, default 10 (matches
Python `minio_limiter`), env `MAX_CONCURRENT_MINIO` |
| Image encoding | Store as-is, no JPEG re-encoding (unlike Python) |
| `img_id` format | `"<kb_id>-<chunk_id>"` — matches Python
task_executor path |
| id function | Single `common.ChunkID(docID, text)`, concatenation
`text+docID` inside hash (matching Python) |
| `removeInternalChunkFields` | Retains `delete(ck,"image")` as
defensive fallback for non-chunker paths |

### Files touched

| File | Change |
|------|--------|
| `internal/common/format.go` | Add `ChunkID(docID, text)` |
| `internal/common/format_test.go` | Add ChunkID golden-value test |
| `internal/ingestion/component/image_uploader.go` | Add `ImageUploader`
type + `DefaultImageUploader` |
| `internal/ingestion/component/chunker/image_upload.go` | Add
`uploadOneImage`, `uploadChunkImages`, `uploadChunkImage`,
`decodeChunkImage`, semaphore |
| `internal/ingestion/component/chunker/image_upload_test.go` | Tests:
upload/drop, skip, no-image, concurrency, missing-id error |
| `internal/ingestion/component/chunker/register.go` | Add
`imageUploadDecorator` (writes `ck["id"]`, runs upload) |
| `internal/ingestion/task/chunk_process.go` | Use `common.ChunkID` for
persist fallback |
| `internal/service/chunk/chunk.go` | Use `common.ChunkID` instead of
`FormatUint` |
| `internal/ingestion/component/chunk_id.go` | **Deleted** (moved to
`common`) |
| `internal/ingestion/task/chunk_builder.go` | **Deleted** (shell, no
callers left) |
| `internal/ingestion/task/chunk_builder_test.go` | **Deleted** (test
migrated to `common/format_test.go`) |

### Verification

```
bash build.sh --test ./internal/service/chunk/... ./internal/common/... ./internal/ingestion/component/... ./internal/ingestion/task/...
→ ok   service/chunk / common / component / chunker / schema / task
```

internal/parser/parser/pptx_parser.go

@@ -25,10 +25,17 @@ import (
 	officeOxide "github.com/yfedoseev/office_oxide/go"
 )
 
-type PPTXParser struct{}
+// PPTXParser parses both .pptx (OOXML) and .ppt (OLE binary)
+// files via the office_oxide backend. The format field controls
+// the container format passed to OpenFromBytes — "pptx" for
+// ZIP-based OOXML presentations and "ppt" for the legacy binary
+// OLE format.
+type PPTXParser struct {
+	format string
+}
 
 func NewPPTXParser() *PPTXParser {
-	return &PPTXParser{}
+	return &PPTXParser{format: "pptx"}
 }
 
 func (p *PPTXParser) String() string {
@@ -39,9 +46,9 @@ func (p *PPTXParser) String() string {
 // plain text. Mirrors the python parser.py:slides branch which
 // forces output_format="json" for the slide family.
 func (p *PPTXParser) ParseWithResult(filename string, data []byte) ParseResult {
-	doc, err := officeOxide.OpenFromBytes(data, "pptx")
+	doc, err := officeOxide.OpenFromBytes(data, p.format)
 	if err != nil {
-		return ParseResult{Err: fmt.Errorf("pptx open: %w", err)}
+		return ParseResult{Err: fmt.Errorf("presentation open: %w", err)}
 	}
 	defer doc.Close()
 
@@ -51,7 +58,7 @@ func (p *PPTXParser) ParseWithResult(filename string, data []byte) ParseResult {
 	}
 
 	// Split on form-feed (the python TxtParser convention used by
-	// ragflow's slide parser) — each block becomes a JSON item.
+	// RAGFlow's slide parser) — each block becomes a JSON item.
 	var items []map[string]any
 	for i, raw := range strings.Split(text, "\f") {
 		trimmed := strings.TrimSpace(raw)
@@ -70,7 +77,7 @@ func (p *PPTXParser) ParseWithResult(filename string, data []byte) ParseResult {
 
 	return ParseResult{
 		OutputFormat: "json",
-		File:         map[string]any{"name": filename, "format": "pptx"},
+		File:         map[string]any{"name": filename, "format": p.format},
 		JSON:         items,
 	}
 }