feat(observability): add InMemoryExporter and TLS timeout support

[wucm667]

Summary

This PR enhances the observability module with the following improvements:

1. InMemoryExporter: A new in-memory span exporter for testing and local debugging, with session-based span tracking and JSON dump support.
2. TLS exporter configurable timeout: Adds a Timeout field to TLSExporterConfig, giving users control over the OTLP HTTP request timeout for both trace and metric TLS exporters.
3. TLS metric export in NewMetricReader: Automatically registers a TLS periodic metric reader when TLS credentials are configured.
4. Refactor: Disambiguates the sdk/trace and otel/trace package imports by aliasing the former as sdktrace.

---

Changed Files

File	Change	Description
configs/observability.go	Modified	Added TLSExporterConfig.Timeout field and corresponding env var
observability/exporter.go	Modified	Added InMemoryExporter, TLS timeout logic, TLS metric reader registration
observability/exporter_test.go	Modified	Added comprehensive unit tests for InMemoryExporter

---

Details

1. InMemoryExporter

InMemoryExporter implements the sdktrace.SpanExporter interface and stores spans in memory. It is designed for testing and local debugging scenarios where a real OTLP backend is not available.

Features:

• Span storage: ExportSpans appends spans to an internal slice and tracks the current TraceID.
• Session tracking: Scans call_llm spans for the gen_ai.session.id attribute and maintains a session → traceID mapping.
• Session-scoped retrieval: GetSpansBySession(sessionID) returns all spans belonging to the given session.
• Full retrieval: GetSpans() returns all collected spans.
• State reset: Reset() / Shutdown() clear all spans and session mappings.
• JSON dump: Dump(sessionID, dir) serializes spans to a JSON file. File naming convention:
  • With session: veadk_trace_{sessionID}_{traceID}.json
  • Without session: veadk_trace_{traceID}.json

Usage example:

exp := observability.NewInMemoryExporter()

// Register with TracerProvider
tp := sdktrace.NewTracerProvider(
    sdktrace.WithBatcher(exp),
)

// Retrieve spans after agent run
spans := exp.GetSpansBySession("my-session-id")

// Export spans to JSON
filePath, err := exp.Dump("my-session-id", "./traces")

2. Configurable TLS Exporter Timeout

New config field:

// configs/observability.go
type TLSExporterConfig struct {
    // ... existing fields ...
    Timeout int `yaml:"timeout"` // timeout in seconds, default 10
}

Environment variable:

OBSERVABILITY_OPENTELEMETRY_TLS_TIMEOUT=30

Behavior:

• When Timeout <= 0, the default of 10s (defaultTLSTimeout) is used.
• The timeout is applied to both the trace exporter (NewTLSExporter) and the metric exporter (NewTLSMetricExporter) via otlptracehttp.WithTimeout / otlpmetrichttp.WithTimeout.
• The previous createTraceClient / createMetricClient wrappers are bypassed for TLS exporters to allow direct option composition.

Helper function:

func tlsTimeout(timeoutSec int) time.Duration {
    if timeoutSec <= 0 {
        return defaultTLSTimeout // 10s
    }
    return time.Duration(timeoutSec) * time.Second
}

3. TLS Metric Export in NewMetricReader

NewMetricReader now automatically registers a TLS periodic metric reader when TLS credentials are present:

if cfg.TLS != nil && cfg.TLS.Endpoint != "" && cfg.TLS.AccessKey != "" && cfg.TLS.SecretKey != "" {
    if exp, err := NewTLSMetricExporter(ctx, cfg.TLS); err == nil {
        readers = append(readers, sdkmetric.NewPeriodicReader(exp))
        log.Info("Exporting metrics to TLS", "endpoint", cfg.TLS.Endpoint, "service_name", cfg.TLS.ServiceName)
    }
}

Previously, TLS metric export was not automatically registered even when TLS credentials were configured. This change brings metric export behavior in line with trace export.

4. Import Alias Refactor

The go.opentelemetry.io/otel/sdk/trace package is now imported as sdktrace to disambiguate it from go.opentelemetry.io/otel/trace. The following function signatures are updated accordingly:

• NewStdoutExporter() (sdktrace.SpanExporter, error)
• NewCozeLoopExporter(...) (sdktrace.SpanExporter, error)
• NewAPMPlusExporter(...) (sdktrace.SpanExporter, error)
• NewTLSExporter(...) (sdktrace.SpanExporter, error)
• NewFileExporter(...) (sdktrace.SpanExporter, error)
• NewMultiExporter(...) (sdktrace.SpanExporter, error)
• multiExporter.ExportSpans(ctx, []sdktrace.ReadOnlySpan)

---

Tests

Added TestInMemoryExporter test suite covering:

Test case	Description
new exporter is empty	Newly created exporter has no spans
export and retrieve spans	Exported spans are retrievable; TraceID is correctly tracked
session tracking	gen_ai.session.id attribute on call_llm spans is mapped to session
reset clears all data	Reset() clears spans and session mappings
shutdown clears all data	Shutdown() clears all state
force flush is no-op	ForceFlush() returns no error
dump to file	Session-scoped dump produces correct JSON file with expected content
dump all spans when session is empty	Empty sessionID dumps all spans; correct filename format

---

Configuration Reference

Full TLS exporter configuration example (config.yaml):

observability:
  opentelemetry:
    tls:
      endpoint: "https://tls.volcengineapi.com"
      region: "cn-beijing"
      topic_id: "your-topic-id"
      access_key: "your-ak"
      secret_key: "your-sk"
      timeout: 30  # new: timeout in seconds

Or via environment variables:

OBSERVABILITY_OPENTELEMETRY_TLS_ENDPOINT=https://tls.volcengineapi.com
OBSERVABILITY_OPENTELEMETRY_TLS_REGION=cn-beijing
OBSERVABILITY_OPENTELEMETRY_TLS_TOPIC_ID=your-topic-id
OBSERVABILITY_OPENTELEMETRY_TLS_ACCESS_KEY=your-ak
OBSERVABILITY_OPENTELEMETRY_TLS_SECRET_KEY=your-sk
OBSERVABILITY_OPENTELEMETRY_TLS_TIMEOUT=30

[sjy3]

@shunjiazhu