[good-first-issue] [Docs] Create SDK Quickstart Guide (docs/SDK_GUIDE.md)

[IyanuOluwaJesuloba]

Summary
The file docs/SDK_GUIDE.md is referenced in the codebase but does not exist. Specifically, in sdk/src/registry.ts line 119:

ts
throw new StellarMindError(
  'find() requires an indexer integration — see docs/SDK_GUIDE.md for setup',
  'NOT_IMPLEMENTED'
);

New developers trying to use the SDK have no guide. This is a documentation issue and is a great first contribution — no Rust or Soroban knowledge required.

What Needs to Be Written
Create docs/SDK_GUIDE.md with the following sections:

Section 1 — Installation

bash
npm install @stellarmind/sdk
# or
yarn add @stellarmind/sdk

Section 2 — Quick Start (5 minutes)
Show the simplest possible working example from zero to first agent query:

ts
import { StellarMind } from '@stellarmind/sdk'

const mind = new StellarMind({ network: 'testnet' })

// Fetch a specific agent
const agent = await mind.registry.getAgent('flux-image-gen-v1')
console.log(`${agent.name} — ${agent.priceDisplay} — ${agent.reputationDisplay}`)

Section 3 — Registering an Agent
Complete working example with all required fields explained:

ts
import { StellarMind, USDC_ISSUER } from '@stellarmind/sdk'
import { Keypair } from '@stellar/stellar-sdk'

const mind = new StellarMind({ network: 'testnet' })
const keypair = Keypair.fromSecret('YOUR_SECRET_KEY') // never commit this

await mind.registry.register({
  id: 'my-agent-v1',
  name: 'My AI Agent',
  description: 'What my agent does',
  capabilities: ['text-generation', 'summarization'],
  pricePerCall: '0.01',          // 0.01 USDC per call
  paymentAsset: 'USDC',
  paymentIssuer: USDC_ISSUER.testnet,
  endpointUrl: 'https://my-api.com/v1',
}, keypair)

Section 4 — Creating a Spending Policy

ts
const policyId = await mind.policy.create({
  agent: 'GBKR...2XPL',          // agent's Stellar address
  maxPerTx: '0.50',               // max $0.50 per single payment
  dailyLimit: '10.00',            // max $10.00 per day total
  asset: 'USDC',
  issuer: USDC_ISSUER.testnet,
}, ownerKeypair)

console.log(`Policy created: ${policyId}`)

Section 5 — Executing an Autonomous Payment

ts
// The AGENT signs this — not the owner
const record = await mind.policy.executePayment({
  policyId: 1n,
  recipient: 'GXXXRECIPIENT...',
  amount: '0.01',
  memo: 'Payment for image generation job #8821',
}, agentKeypair)

console.log(`Paid ${record.amount} on ledger ${record.ledger}`)

Section 6 — Checking Remaining Allowance

tsconst remaining = await mind.policy.remainingAllowanceDisplay(1n)
console.log(remaining) // "8.5000000 USDC"

Section 7 — Error Handling

tsimport { StellarMindError, ErrorCodes } from '@stellarmind/sdk'

try {
  const agent = await mind.registry.getAgent('unknown-id')
} catch (err) {
  if (err instanceof StellarMindError) {
    switch (err.code) {
      case ErrorCodes.AGENT_NOT_FOUND:
        console.log('Agent does not exist')
        break
      case ErrorCodes.NETWORK_ERROR:
        console.log('Could not reach Stellar RPC:', err.message)
        break
      case ErrorCodes.EXCEEDS_DAILY_LIMIT:
        console.log('Daily spending limit reached')
        break
    }
  }
}

Section 8 — Network Configuration

ts
// Testnet (default for development)
const mind = new StellarMind({ network: 'testnet' })

// Mainnet (production)
const mind = new StellarMind({ network: 'mainnet' })

// Custom RPC URL
const mind = new StellarMind({
  network: 'testnet',
  rpcUrl: 'https://my-custom-rpc.example.com',
})

Section 9 — TypeScript Types Reference

List all exported types with a one-line description each:

Agent — full agent struct returned from registry
SpendingPolicy — full policy struct
RegisterAgentParams — input for registry.register()
CreatePolicyParams — input for policy.create()
ExecutePaymentParams — input for policy.executePayment()
PaymentRecord — returned from executePayment()
StellarMindConfig — SDK constructor config
Network — 'mainnet' | 'testnet' | 'futurenet'

Acceptance Criteria

File docs/SDK_GUIDE.md created
All 9 sections present
Every code example is syntactically correct TypeScript (no fake syntax)
Import statements are accurate and match what sdk/src/index.ts actually exports
All USDC_ISSUER references use the correct exported constant
No placeholder text like "TODO" or "coming soon" left in the guide
The guide reads clearly for a developer who has never used StellarMind before

Tips

Read sdk/src/index.ts to see exactly what is exported — only document real exports
Read sdk/src/types.ts for the full list of types
Test every code snippet mentally — if it would throw a TypeScript error, fix it

Estimated Effort
Small (2–4 hours)

[xxCodexIAxx]

Submitted PR: #10

I completed the SDK quickstart guide requested in this bounty.

Please send the bounty payout to my Base wallet: 0x776CbBb63D81c08B4090DB503eAE7FDb8fBd7c6f