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/opencode-plugin/src/utils.ts

@@ -0,0 +1,97 @@
+import type { JsonValue } from "agentlens-sdk";
+
+export function truncate(str: string, maxLength: number): string {
+  if (str.length <= maxLength) return str;
+  return str.slice(0, maxLength) + "... [truncated]";
+}
+
+export function extractToolMetadata(
+  tool: string,
+  args: unknown,
+): Record<string, unknown> {
+  const a = args as Record<string, unknown> | null | undefined;
+  if (!a || typeof a !== "object") return {};
+
+  switch (tool) {
+    case "read":
+    case "mcp_read":
+      return { filePath: a["filePath"] };
+
+    case "write":
+    case "mcp_write":
+      return { filePath: a["filePath"] };
+
+    case "edit":
+    case "mcp_edit":
+      return { filePath: a["filePath"] };
+
+    case "bash":
+    case "mcp_bash":
+      return {
+        command: truncate(String(a["command"] ?? ""), 200),
+      };
+
+    case "glob":
+    case "mcp_glob":
+      return { pattern: a["pattern"] };
+
+    case "grep":
+    case "mcp_grep":
+      return { pattern: a["pattern"], path: a["path"] };
+
+    case "task":
+    case "mcp_task":
+      return {
+        category: a["category"],
+        description: a["description"],
+      };
+
+    default:
+      return {};
+  }
+}
+
+const MODEL_COSTS: Record<string, { input: number; output: number }> = {
+  "claude-opus-4-20250514": { input: 15, output: 75 },
+  "claude-sonnet-4-20250514": { input: 3, output: 15 },
+  "claude-haiku-3-20250307": { input: 0.25, output: 1.25 },
+  "gpt-4o": { input: 2.5, output: 10 },
+  "gpt-4o-mini": { input: 0.15, output: 0.6 },
+  "gpt-4-turbo": { input: 10, output: 30 },
+  "o3-mini": { input: 1.1, output: 4.4 },
+};
+
+export function getModelCost(
+  modelId: string,
+): { input: number; output: number } | undefined {
+  const direct = MODEL_COSTS[modelId];
+  if (direct) return direct;
+
+  for (const [key, cost] of Object.entries(MODEL_COSTS)) {
+    if (modelId.includes(key)) return cost;
+  }
+  return undefined;
+}
+
+/** Coerce arbitrary values into SDK-compatible `JsonValue`, stringifying unknowns. */
+export function safeJsonValue(value: unknown): JsonValue {
+  if (value === null || value === undefined) return null;
+  if (
+    typeof value === "string" ||
+    typeof value === "number" ||
+    typeof value === "boolean"
+  ) {
+    return value;
+  }
+  if (Array.isArray(value)) {
+    return value.map((v) => safeJsonValue(v));
+  }
+  if (typeof value === "object") {
+    const result: Record<string, JsonValue> = {};
+    for (const [k, v] of Object.entries(value as Record<string, unknown>)) {
+      result[k] = safeJsonValue(v);
+    }
+    return result;
+  }
+  return String(value);
+}