feat: add solo stacker test instructions

[matteojug-stacks]

Add instructions (and scripts) to test spox with solo stacker(s) using sBTC devenv.

Because of low PoX payments + high suggested fees in sBTC devenv, it currently require using devenv from stacks-sbtc/sbtc#1988.

Testing Information

Tested the instructions locally

[Copilot]

Pull request overview

Adds a self-contained “solo stackers” demo under tests/ to exercise sPoX against an sBTC devenv, including a TS-based stacking loop, shell helpers for environment setup, and a sample spox.toml config.

Changes:

• Add a solo-stacker TS demo (tsx) that stack-stx / stack-extend loops for multiple accounts.
• Add helper config + shell script to derive signers xonly key and deposit addresses and export required env vars.
• Add a small tests/ Node workspace (package.json + pnpm-lock.yaml) and documentation for running the demo.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
tests/solo/spox.toml	Sample config for local sPoX + two monitored deposits (alice/bob)
tests/solo/populate_env.sh	Script to compute/export env vars used by sPoX and the demo stackers
tests/solo/demo.ts	TS stacking demo: stack/extend loop + info command
tests/common.ts	Shared TS utilities: logging, env parsing, wait-for-setup, signer client
tests/README.md	Step-by-step instructions to run devenv, fund accounts, run demo + sPoX
tests/package.json	Declares Node deps for running the TS demo via pnpm/tsx
tests/pnpm-lock.yaml	Lockfile for the tests/ Node dependencies
tests/.gitignore	Ignores node_modules/ under tests/
tests/.env	Default env values for local Stacks RPC + reward cycle length

Files not reviewed (1)

• tests/pnpm-lock.yaml: Language not supported

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.