Add JSDoc comments to AgentBillClient (Node.js SDK)

[marketinglior-pixel]

What needs to be done:
Add JSDoc comments to the AgentBillClient class in the Node.js SDK so that IDE autocomplete works for users.

Where: sdk/node/ — find the main client class file.

What to document:

• The class itself
• preflight() method — parameters and return value
• record() method — parameters and return value

Example format:

/**
 * Check budget before running an agent.
 * @param {string} agentId - Your agent identifier
 * @param {number} estimatedUnits - Expected billable units
 * @returns {{ approved: boolean, reason?: string }}
 */
How to test: Open the file in VS Code — you should see autocomplete hints when using client.preflight(.

Good for: Someone familiar with JavaScript/TypeScript. No server needed.