docs: add class 1 stablecoin issuance walkthrough

docs/class-1-stablecoin-issuance-walkthrough.md

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+# Class 1 — Stablecoin Issuance Walkthrough
+
+## Purpose
+
+Class 1 demonstrates the minimum lifecycle of a Stellar classic asset used as a fictional stablecoin.
+
+It shows how an issuer creates an asset, how a holder consents to receive it through a trustline, and how payments fail when that consent does not exist.
+
+## Actors
+
+- `issuer`: the account that defines and issues the asset.
+- `distributor`: the operational account that receives the initial supply.
+- `holder`: the user account that must explicitly trust the asset before receiving it.
+
+## Asset Identity
+
+A Stellar classic asset is identified by both its code and its issuer:
+
+```text
+CODE:ISSUER
+```
+
+For example:
+
+```text
+cBRL:G...
+```
+
+This means that `cBRL` alone is not enough to identify the asset. The issuer public key is part of the asset identity.
+
+## Class 1 Flow
+
+1. Create and fund fresh testnet accounts.
+2. Define the fictional `cBRL` asset.
+3. The distributor creates a trustline to `cBRL`.
+4. The issuer sends the initial supply to the distributor.
+5. The distributor attempts to pay a holder with no trustline.
+6. The payment fails with `op_no_trust`.
+7. The holder creates a trustline.
+8. The distributor pays the holder successfully.
+
+## What This Demonstrates
+
+Class 1 demonstrates three core Stellar asset concepts:
+
+- Asset issuance is performed by the issuer account.
+- A receiver must explicitly consent to hold a non-native asset through a trustline.
+- Without a trustline, a payment fails with `op_no_trust`.
+
+## What This Does Not Cover
+
+This is an educational testnet simulation. It does not cover the full requirements of a production-grade stablecoin, such as:
+
+- reserve management;
+- redemption;
+- compliance and KYC;
+- custody;
+- audits;
+- governance of issuer keys;
+- legal enforceability of the peg.
+
+## Why This Matters
+
+For regulated or semi-regulated assets, such as stablecoins, tokenized collateral, or energy settlement instruments, the key question is not only:
+
+```text
+What is the token?
+```
+
+The stronger question is:
+
+```text
+Who controls the asset, and where is that authority encoded?
+```
+
+Class 1 answers the first part of that question by showing issuer identity and holder consent.
+
+## Related Files
+
+- `scripts/reproduce/class-1.ts`
+- `src/operations/trustline.ts`
+- `src/operations/issue.ts`
+- `src/lib/tx.ts`
+- `docs/control-spectrum.md`
+- `docs/architecture.md`