### Summary
The Go backend Agent component was not returning artifacts produced by
the CodeExec tool. While the Python agent collects the "`_ARTIFACTS`"
envelope from tool responses and appends artifact markdown to the final
content, the Go agent only returned the assistant text, so generated
images were missing from the chat output.
### Changes
- Wire `react.WithMessageFuture()` in `runEinoReActAgent` and store the
resulting `MessageFuture` in the invocation context.
- After the ReAct loop finishes, drain the future and extract
``_ARTIFACTS`` entries from every tool response message.
- Support reading the tool payload from both `msg.Content` and
`msg.UserInputMultiContent` to match eino's tool contract.
- De-duplicate artifacts by URL and render images as `!` and other files
as download links.
- Add `agent_artifact_test.go` with a regression test that simulates a
CodeExec-style tool response carrying an image artifact and verifies it
is collected and formatted.
### Verification
- `go test ./internal/agent/component/... -run
TestAgent_ReActAgent_CollectsArtifactsFromCodeExecTool` passes.
- `go test ./internal/agent/component/... -count=1` compiles; the only
failure is an unrelated DNS-pinning timeout test
(`TestInvoke_ProxyDNSPin`).
- `gofmt` clean for modified files.
### Related
Fixes the behavior shown in the screenshot where the Go agent ignored
the CodeExec-generated PNG artifact.
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>
Replaces the Python agent canvas runtime with a Go implementation that
runs inside `cmd/server_main`.
The canvas compiles into an eino Workflow that pauses on wait-for-user
via native Interrupt/Resume (no sentinel flag) and resumes from a
Redis-backed CheckPointStore.
All 21 Python agent components and ~35 tools are ported with functional
parity.
Sandbox providers now read their JSON config from the admin-panel
system_settings table with env fallback.
234 files / +35,413 / -6,111. All Go files are gofmt-clean (CI gate
added); drops the v2 DSL E2E step and the gap-analysis plan (both
redundant after the port ships).
## Type of change
- [x] Refactoring
- [x] New feature
- [x] Bug fix
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude <noreply@anthropic.com>
