## Summary
Three groups of changes across the Go ingestion pipeline:
### 1. DOCX parsing improvements
- **docx_parser.go**: Enhanced DOCX parsing with better structure
extraction and media handling
- **docx_parser_cgo_test.go**, **docx_parser_test.go**: Companion tests
- **office_parsers_no_cgo.go**: Stub sync for non-CGO builds
### 2. Email (.eml) parsing: base64 Content-Transfer-Encoding decoding
- **email_parser.go** (`decodeCTE`): Added Content-Transfer-Encoding
decoding for base64 and quoted-printable. Go's `mime/multipart.Reader`
does not decode Content-Transfer-Encoding automatically, so attachments
with `Content-Transfer-Encoding: base64` remained base64-encoded in the
output. The new `decodeCTE` helper is called after reading each
multipart part's raw bytes in `readMailBody`, mirroring Python's
`part.get_payload(decode=True)`.
- **email_parser_test.go**: Two new tests — simple base64 attachment and
nested multipart/alternative with base64 attachment.
### 3. Extractor LLM driver fix + ModelDriver consolidation
- **extractor.go**: Fixed a bug where the Extractor component used
`ModelFactory.CreateModelDriver()`, which creates bare model instances
without API keys or provider configuration. Switched to
`models.GetPreconfiguredDriver()` which resolves the actual
pre-configured driver from `ProviderManager`, matching the codepath used
by `llm.go`. This fixes auto keyword/question extraction in DSL
pipelines that require LLM calls.
- **get_driver.go** (new): Extracted shared `GetPreconfiguredDriver()`
from `llm.go:newChatModelDriver()` so both `llm.go` and `extractor.go`
use the same codepath.
- **get_driver_test.go** (new): Tests for the shared driver resolution.
- **llm.go**: Replaced inline driver resolution with
`models.GetPreconfiguredDriver()`.
### 4. Chunker fixes and observability
- **group.go** (`extractLineRecords`): Fixed to also read `markdown` and
`html` payload keys — previously it only read `text`/`content`, causing
GroupTitleChunker to silently return empty results for markdown-format
parser output.
- **common.go** (`compileDelimPattern`): Aligned with Python's
`_compile_delimiter_pattern` — only backtick-wrapped delimiters produce
an active regex pattern; plain delimiters are not compiled into the
split regex.
- **token.go** (`applyChildrenDelim`): Set `DocType` and `CKType` to
`"text"` on created ChunkDocs so the token-size merge path correctly
identifies and merges text segments.
- **parser.go**, **extractor.go**, **tokenizer.go**, **group.go**,
**hierarchy.go**: Added debug-level logging for pipeline diagnostics.
- **parser_dispatch_test.go**, **group_test.go**: New tests.
## Verification
- All Go tests pass: `bash build.sh --test ./internal/parser/parser/...`
and `bash build.sh --test ./internal/ingestion/component/...`
- Build succeeds: `bash build.sh --go`
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