feat(usage): implement usage tracking infrastructure across executors

- Added `LoggerPlugin` to log usage metrics for observability.
- Introduced a new `Manager` to handle usage record queuing and plugin registration.
- Integrated new usage reporter and detailed metrics parsing into executors, covering providers like OpenAI, Codex, Claude, and Gemini.
- Improved token usage breakdown across streaming and non-streaming responses.

internal/runtime/executor/gemini_cli_executor.go

@@ -54,6 +54,7 @@ func (e *GeminiCLIExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth
 	if err != nil {
 		return cliproxyexecutor.Response{}, err
 	}
+	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
 
 	from := opts.SourceFormat
 	to := sdktranslator.FromString("gemini-cli")
@@ -117,6 +118,7 @@ func (e *GeminiCLIExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth
 		_ = resp.Body.Close()
 		appendAPIResponseChunk(ctx, e.cfg, data)
 		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+			reporter.publish(ctx, parseGeminiCLIUsage(data))
 			var param any
 			out := sdktranslator.TranslateNonStream(respCtx, to, from, attemptModel, bytes.Clone(opts.OriginalRequest), payload, data, &param)
 			return cliproxyexecutor.Response{Payload: []byte(out)}, nil
@@ -139,6 +141,7 @@ func (e *GeminiCLIExecutor) ExecuteStream(ctx context.Context, auth *cliproxyaut
 	if err != nil {
 		return nil, err
 	}
+	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
 
 	from := opts.SourceFormat
 	to := sdktranslator.FromString("gemini-cli")
@@ -215,6 +218,9 @@ func (e *GeminiCLIExecutor) ExecuteStream(ctx context.Context, auth *cliproxyaut
 				for scanner.Scan() {
 					line := scanner.Bytes()
 					appendAPIResponseChunk(ctx, e.cfg, line)
+					if detail, ok := parseGeminiCLIStreamUsage(line); ok {
+						reporter.publish(ctx, detail)
+					}
 					if bytes.HasPrefix(line, dataTag) {
 						segments := sdktranslator.TranslateStream(respCtx, to, from, attempt, bytes.Clone(opts.OriginalRequest), reqBody, bytes.Clone(line), &param)
 						for i := range segments {
@@ -239,6 +245,7 @@ func (e *GeminiCLIExecutor) ExecuteStream(ctx context.Context, auth *cliproxyaut
 				return
 			}
 			appendAPIResponseChunk(ctx, e.cfg, data)
+			reporter.publish(ctx, parseGeminiCLIUsage(data))
 			var param any
 			segments := sdktranslator.TranslateStream(respCtx, to, from, attempt, bytes.Clone(opts.OriginalRequest), reqBody, data, &param)
 			for i := range segments {