chore: add AGENTS.md + CLAUDE.md, clean JS cruft

.gitignore

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-bower_components/
-.psci_modules/
-output/
-.psc-ide-port
-.spago/
+/.*
+!/.gitignore
+!/.github/
+/output/

AGENTS.md

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+# AGENTS.md
+
+A PureScript→Lua FFI fork in the [`purescript-lua`](https://github.com/Unisay/purescript-lua) package set. Generated code targets **Lua 5.1**.
+
+## Commands
+
+All commands run inside the nix dev shell:
+
+- Build: `nix develop -c ./scripts/build`
+- Test (only if the fork has `scripts/test`): `nix develop -c bash ./scripts/test`
+- Lint: `nix develop -c luacheck --quiet --std lua51 --no-unused-args dist/` (this fork has no hand-written FFI, so luacheck runs over the generated `dist/`)
+
+## Lua 5.1 target
+
+The output runs on Lua 5.1, which is stricter than 5.3:
+
+- No `table.unpack`, `bit32`, `utf8`, or the `//` operator. `math.pow` and `math.atan2` do exist.
+- Array-style tables are 1-indexed: the first element is `t[1]`, not `t[0]`.
+- `unit` is `{}`, never `nil`: a `nil` table element silently disappears, which would collapse `Array Unit` into an empty table.
+- Lua 5.1 mangles some Lua 5.3 string escapes, so keep FFI string escapes 5.1-safe.
+
+## FFI
+
+This fork is pure PureScript over `unsafeCoerce` and ships no hand-written Lua FFI of its own. The set-wide rule, for forks that do have FFI: every exported value must be parenthesised (`return { name = (<value>), ... }`), because pslua's foreign-file parser requires it.
+
+## Toolchain
+
+`flake.nix` pins everything through [`purescript-overlay`](https://github.com/thomashoneyman/purescript-overlay): purs 0.15.16 (`purs-bin.purs-0_15_16`), spago 0.21.0 (`spago-bin.spago-0_21_0`), Lua 5.1 (`lua51Packages`). The `pslua` input tracks `github:Unisay/purescript-lua`; keep `flake.lock` reasonably current, since a long-stale pslua pin won't create the `--lua-output-file` directory and CI fails.
+
+## Releasing
+
+Tag-driven, with no GitHub Release or changelog entry. The full conventions live in the [package-set repo](https://github.com/Unisay/purescript-lua-package-sets/blob/master/CONTRIBUTING.md): push an annotated tag on `master`, bump this fork's `version` in the package set's `src/packages.dhall`, refresh `latest-compatible-sets.json`, and push a `psc-*` set tag.
+
+## Decisions
+
+Cross-cutting decisions are recorded as ADRs in the [package-set repo](https://github.com/Unisay/purescript-lua-package-sets/tree/master/docs/adr). Read them before a decision that affects the set, and add one after making such a decision.

CLAUDE.md

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+@AGENTS.md