## Summary
Add the Go implementation of `POST
/api/v1/datasets/{dataset_id}/documents/{document_id}/chunks`.
This wires the full create-chunk path in Go:
- router and handler registration
- request/response structs
- chunk creation service logic
- embedding generation
- chunk insert into doc engine
- chunk/token counter increment
- `tag_feas` validation
- `image_base64` decoding and chunk image storage/merge
- unit tests for handler and service
## Testing
Unit tests:
- `/usr/local/go/bin/go test ./internal/handler`
- `/usr/local/go/bin/go test ./internal/service/chunk`
- `/usr/local/go/bin/go test ./internal/service`
- `/usr/local/go/bin/go test ./...`
All passed locally.
Manual curl checks:
- basic text chunk: Go passed
- chunk with `important_keywords` / `questions` / `tag_kwd` /
`tag_feas`: Go passed
- blank content validation: Go matched expected `code=102`
- invalid `image_base64` validation: Go matched expected `code=102`
- image upload and repeated image upload / merge path: Go passed twice
### What problem does this PR solve?
- OpenTelemetry integration
- Checkpoint conformance tests
- State inspector API
- Callbacks
- A series of fault injection tests
- Pregel integration tests
### Type of change
- [x] Refactoring
### What problem does this PR solve?
- Tools management
- Pregel engine wrapper for better usage
- UT race
- Coding style
### Type of change
- [x] Refactoring
Refactor the Go agent port's logging so every log line — gin access,
agent canvas events, harness warnings, fatal boot errors — flows through
a single common.Logger (zap) backed by a rotated file, with structured
fields, level filtering, and configurable rotation.
---------
Co-authored-by: Claude <noreply@anthropic.com>
### What problem does this PR solve?
core module for agent layer built on top of graph engine #16039
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
go-version of Pregel-based BSP engine
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
