feat: bring st to the canon and add ST unit tests

[Unisay]

Brings purescript-lua-st onto the package-set canon and gives it a working Lua test suite.

Scaffolding. Replaces the JavaScript-era tooling (npm/bower CI, easy-purescript flake, .eslintrc, package.json, .js FFI) with the canon: an overlay flake pinning purs 0.15.16 / spago 0.21.0 / Lua 5.1 and pslua at the current main, hardened CI, scripts/build, AGENTS.md + CLAUDE.md, a clean .gitignore, and the purescript-lua org package-set URL.

Tests.spago-test.dhall compiles test/Main.purs to dist/test.lua through pslua; scripts/test runs it under Lua 5.1. The suite asserts ST.run with STRef new/read/write/modify (sum of squares, write-then-read, modify-returns-new).

Fixes found along the way.Control.Monad.ST.Global imports Effect, so effect is now a declared dependency; and one mkSTFn10 line in the Uncurried FFI was over 120 cols, so it is wrapped to keep luacheck --std lua51 clean.

Verified locally: build, scripts/test (all ST tests passed), and luacheck all green.

[Copilot]

Pull request overview

This PR modernizes purescript-lua-st to match the purescript-lua package-set “canon” (Nix flake + Spago + pslua backend) and introduces a runnable Lua 5.1 unit test suite for core ST/STRef behavior.

Changes:

• Replace legacy JS-era tooling (npm/bower/eslint/pulp + JS FFI remnants) with a Nix flake dev shell and hardened GitHub Actions CI.
• Add a Spago test config and shell test runner that builds test/Main.purs to dist/test.lua and runs it under Lua 5.1.
• Update package metadata/docs (Spago deps, package-set URL, README, contributor/agent docs).

Reviewed changes

Copilot reviewed 17 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/Main.purs	Adds unit tests for ST.run and STRef new/read/write/modify, plus a success log message.
src/Control/Monad/ST/Uncurried.lua	Wraps mkSTFn10 across lines to satisfy luacheck line-length constraints.
src/Control/Monad/ST/Uncurried.js	Removes JS backend FFI implementation for ST uncurried helpers.
src/Control/Monad/ST/Internal.js	Removes JS backend FFI implementation for core ST operations and STRef primitives.
src/Control/Monad/ST/.editorconfig	Removes per-subdir EditorConfig (tooling is centralized elsewhere).
spago.dhall	Adds effect dependency and updates pslua backend entry/output settings.
spago-test.dhall	Adds a test Spago config to compile Test.Main into dist/test.lua and include test deps.
scripts/test	Adds a CI-friendly test runner that builds via spago-test.dhall and runs Lua 5.1.
scripts/build	Hardens build script (set -euo pipefail) and uses plain spago build.
README.md	Updates project identity and positioning as the Lua fork, plus current CI/docs links.
packages.dhall	Points the Lua package-set URL at the purescript-lua org location.
package.json	Removes legacy npm/pulp/eslint tooling configuration.
flake.nix	Replaces easy-purescript tooling with purescript-overlay, pins toolchain, and adds nixConfig caches.
flake.lock	Updates lockfile to match the new flake inputs/toolchain.
CLAUDE.md	Adds a pointer to AGENTS.md for agent instructions.
AGENTS.md	Documents the Lua 5.1 target, FFI conventions, and canonical build/test/lint commands.
.gitignore	Cleans up ignores after removing node/bower-era artifacts.
.github/workflows/ci.yml	Replaces Node-based CI with Nix-based build/test/luacheck steps.
.eslintrc.json	Removes legacy ESLint configuration.

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