docs(examples): add CosmWasm contract examples and end-to-end deploy walkthrough

[danbaruka]

Summary

Safrochain ships with CosmWasm enabled (see wasmbindings/ and the x/cw-hooks module), but the repository contains no runnable CosmWasm contract examples or a walkthrough that takes a new developer from cargo new to a deployed contract on a local Safrochain node. New builders coming from the broader CosmWasm ecosystem currently have to piece this together themselves.

Goal

Add an examples/cosmwasm/ directory with at least three small, self-contained reference contracts and a step-by-step guide that uses safrochaind to compile, upload, instantiate, and execute them against a local node.

Suggested example contracts

1. counter/ — the classic Hello-World: Increment, Reset, GetCount. Demonstrates state, messages, queries, and unit testing with cw-multi-test.
2. cw20-mintable/ — a minimal mintable CW20 token. Demonstrates the standard token interface and how to mint/transfer/query balances.
3. clock-counter/ — a contract registered with x/clock that auto-increments on every block. Shows how to use Safrochain's custom clock module — this is one of the chain's differentiators and currently has no public example.

Optional bonus:

4. cw-hooks-listener/ — subscribes to events via x/cw-hooks. Same rationale as above: it's a Safrochain-specific feature with no published example.

Suggested walkthrough (examples/cosmwasm/README.md)

1. Prerequisites (rustup, wasm32-unknown-unknown target, cargo-generate, safrochaind)
2. Build with cargo wasm + optional cosmwasm/optimizer Docker image
3. safrochaind tx wasm store … to upload the bytecode (with gas/fee guidance using usaf)
4. safrochaind tx wasm instantiate …
5. safrochaind tx wasm execute … and safrochaind query wasm contract-state smart …
6. How to register the contract with x/clock or x/cw-hooks where applicable
7. Troubleshooting (gas estimation, wasm size limit, query vs execute)

Why this matters

• Lowers the barrier to entry. New CosmWasm developers can clone the repo and have a working contract on a Safrochain devnet in under 30 minutes.
• Documents Safrochain-specific features. x/clock and x/cw-hooks are real differentiators but invisible to anyone who hasn't read the Go code. Examples are the most credible form of documentation for them.
• Drives adoption. Most chains compete for contract developers on tooling and examples. A complete examples/ directory is one of the highest-leverage docs investments.
• Stress-tests the chain. Maintaining runnable examples surfaces breakage from SDK / wasmd / wasmvm bumps before integrators hit it.

Acceptance criteria

• examples/cosmwasm/<name>/ directory per contract, each independently buildable
• Each contract has unit tests passing under cargo test
• Each contract has a Makefile or justfile with build, optimize, store, instantiate, execute targets
• Top-level examples/cosmwasm/README.md walks through the full local-node flow with copy-pasteable commands
• Examples reference usaf for fees and safro-testnet-1 as the chain ID, matching the main README

Why this is a good first issue

Each contract can be tackked independently — a newcomer can pick "counter" or "cw20-mintable" without needing deep chain knowledge, and the Rust side is well-trodden territory in the CosmWasm community. Comment to claim one.

[Karry2019web]

Claiming this issue 🎯

I'll be working on the CosmWasm examples as described:

1. counter/ — Classic increment/decrement/reset contract with full unit tests
2. cw20-mintable/ — Minimal mintable CW20 token
3. clock-counter/ — Contract registered with x/clock that auto-increments every block
4. cw-hooks-listener/ (bonus) — Contract subscribing to staking events via x/cw-hooks

I'll include:

• Full Rust source for each contract
• Unit tests passing under cargo test
• A top-level walkthrough README with copy-pasteable safrochaind commands
• Makefile targets per contract

Expected delivery: EOD.

[Karry2019web]

/attempt

PR #56 submitted with:

• counter contract (basic CRUD)
• cw20-mintable token
• clock-counter (x/clock integration)
• cw-hooks-listener (bonus: x/cw-hooks staking events)
• Full walkthrough README with copy-pasteable commands