Fix flake build, enum query params, and CI

[dz0ny]

No description provided.

[Copilot]

Pull request overview

This PR improves reliability of enum handling during Elm SDK generation and makes the project easier to build/test consistently in CI and via Nix flakes.

Changes:

• Fix named-enum lookup to be order-insensitive by sorting enum variant keys before dictionary lookup.
• Add a regression test ensuring named enum query params use enum-to-string helpers even when enum variant order differs.
• Update build tooling: introduce a Nix flake-based build (with Elm dep pinning artifacts), adjust Volta’s Node pin, and expand CI triggers.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/Test/OpenApi/Generate.elm	Adds regression test for enum query params + new expectOccurrenceCount helper.
src/CliMonad.elm	Sorts enum variants before lookup to match how enums are keyed during extraction.
package.json	Updates Volta pinned Node version.
flake.nix	Reworks flake to build the CLI with Bun + Elm deps via fetchElmDeps, and exposes packages/apps.
cli/registry.dat	Adds Elm package registry data needed for reproducible Elm dependency fetching in Nix.
cli/elm-srcs.nix	Adds pinned Elm dependency sources/hashes for Nix builds.
.gitignore	Ignores result symlink from nix build.
.github/workflows/ci.yaml	Runs CI on pushes to main in addition to PRs.

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