feat: TypeScript SDK (agentlens-sdk) and OpenCode plugin (opencode-agentlens)

- packages/sdk-ts: BatchTransport, TraceBuilder, models, decision helpers
  Zero external deps, native fetch, ESM+CJS output
- packages/opencode-plugin: OpenCode plugin with hooks for:
  - Session lifecycle (create/idle/error/delete/diff)
  - Tool execution capture (before/after -> TOOL_CALL spans + TOOL_SELECTION decisions)
  - LLM call tracking (chat.message -> LLM_CALL spans with model/provider)
  - Permission flow (permission.ask -> ESCALATION decisions)
  - File edit events
  - Model cost estimation (Claude, GPT-4o, o3-mini pricing)

packages/sdk-ts/src/transport.ts

@@ -0,0 +1,77 @@
+import type { TracePayload } from "./models.js";
+
+export interface BatchTransportOptions {
+  apiKey: string;
+  endpoint: string;
+  maxBatchSize?: number;
+  flushInterval?: number;
+}
+
+export class BatchTransport {
+  private readonly apiKey: string;
+  private readonly endpoint: string;
+  private readonly maxBatchSize: number;
+  private readonly flushInterval: number;
+  private buffer: TracePayload[] = [];
+  private timer: ReturnType<typeof setInterval> | null = null;
+
+  constructor(options: BatchTransportOptions) {
+    this.apiKey = options.apiKey;
+    this.endpoint = options.endpoint.replace(/\/+$/, "");
+    this.maxBatchSize = options.maxBatchSize ?? 10;
+    this.flushInterval = options.flushInterval ?? 5_000;
+
+    this.timer = setInterval(() => {
+      void this._doFlush();
+    }, this.flushInterval);
+  }
+
+  add(trace: TracePayload): void {
+    this.buffer.push(trace);
+    if (this.buffer.length >= this.maxBatchSize) {
+      void this._doFlush();
+    }
+  }
+
+  async flush(): Promise<void> {
+    await this._doFlush();
+  }
+
+  async shutdown(): Promise<void> {
+    if (this.timer !== null) {
+      clearInterval(this.timer);
+      this.timer = null;
+    }
+    await this._doFlush();
+  }
+
+  private async _doFlush(): Promise<void> {
+    if (this.buffer.length === 0) {
+      return;
+    }
+
+    const batch = this.buffer.splice(0, this.buffer.length);
+
+    try {
+      const response = await fetch(`${this.endpoint}/api/traces`, {
+        method: "POST",
+        headers: {
+          Authorization: `Bearer ${this.apiKey}`,
+          "Content-Type": "application/json",
+        },
+        body: JSON.stringify({ traces: batch }),
+      });
+
+      if (!response.ok) {
+        const text = await response.text().catch(() => "");
+        console.warn(
+          `AgentLens: Failed to send traces (HTTP ${response.status}): ${text.slice(0, 200)}`,
+        );
+      }
+    } catch (error: unknown) {
+      const message =
+        error instanceof Error ? error.message : String(error);
+      console.warn(`AgentLens: Failed to send traces: ${message}`);
+    }
+  }
+}