fix(callbacks): replace sonic JSON path for Go 1.24 compatibility

[liusonglei796]

Background\nGo 1.24 environments can hit linker/runtime issues via transitive github.com/bytedance/sonic/loader dependency.\n\n## Changes\n- callbacks/langsmith: replace sonic marshal/unmarshal with encoding/json\n- callbacks/langfuse: replace sonic marshal calls with encoding/json\n- run go mod tidy in both callback submodules\n\n## Scope\nThis PR only updates callback submodules where sonic was directly imported and used for JSON serialization.\n\n## Notes\nMainline behavior is preserved; only JSON codec implementation is changed for compatibility.

[Copilot]

Pull request overview

Updates the callback submodules’ JSON serialization approach to avoid direct use of github.com/bytedance/sonic in callback handlers, aiming to improve Go 1.24 compatibility.

Changes:

• callbacks/langsmith: replaced sonic marshal/unmarshal usage in handler/state serialization with encoding/json.
• callbacks/langfuse: replaced sonic marshal usage in handler paths with encoding/json.
• callbacks/langfuse: updated module metadata (go.mod/go.sum) after dependency cleanup.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
callbacks/langsmith/langsmith.go	Switches input/output JSON serialization in callback handler from sonic to encoding/json.
callbacks/langsmith/flow_trace.go	Switches span/state serialization from sonic to encoding/json.
callbacks/langfuse/langfuse.go	Switches handler JSON serialization from sonic to encoding/json (including streaming paths).
callbacks/langfuse/go.mod	Removes direct sonic requirement and updates indirect dependency set.
callbacks/langfuse/go.sum	Reflects dependency graph changes from go mod tidy.

Comments suppressed due to low confidence (1)

callbacks/langsmith/langsmith.go:32

• This module still depends on github.com/bytedance/sonic: callbacks/langsmith/client.go imports it and uses sonic.Marshal/sonic.Unmarshal, and callbacks/langsmith/go.mod still requires it. If the goal is Go 1.24 compatibility by avoiding sonic/loader, the remaining usage/dependency should also be migrated to encoding/json (or removed) and go mod tidy re-run so sonic drops from the module.

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"runtime/debug"
	"sync"
	"time"

	"github.com/cloudwego/eino/callbacks"
	"github.com/cloudwego/eino/schema"
	"github.com/google/uuid"
)

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[Copilot]

github.com/bytedance/sonic and github.com/bytedance/sonic/loader are still present in this module’s go.mod (even if indirect). If the intent is to eliminate Go 1.24 linker/runtime issues related to sonic/loader, this module will likely still pull it in via dependencies (e.g., github.com/cloudwego/eino-ext/libs/acl/langfuse in this repo currently imports sonic). Consider updating that dependency to stop using sonic and/or removing these indirect requirements once the dependency graph no longer needs them.

Suggested change

	github.com/bytedance/sonic v1.14.1 // indirect
	github.com/bytedance/sonic/loader v0.3.0 // indirect