feat: add Nix flake dev environment

[yuuhikaze]

Summary

Adds a Nix flake for a reproducible development environment, mainly aimed at NixOS users who can't run the npm-bundled Electron binary out of the box (missing dynamic libraries, no hardcoded RPATHs).

What it does

The flake provides a dev shell with Node.js and a NixOS-patched Electron binary. It sets ELECTRON_EXEC_PATH so electron-vite picks up the system Electron instead of the one from node_modules — no LD_LIBRARY_PATH hacks needed.

Includes a .envrc for direnv users: run direnv allow once and the environment loads automatically every time you cd into the project.

For non-NixOS users

This changes nothing. The flake and .envrc are inert unless you have Nix installed. The regular npm install && npm run dev workflow is unchanged.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added a Nix flake–based development environment, providing a ready-to-use shell with Node.js and Electron (recommended for NixOS users).
• Documentation
  • Expanded the README with NixOS-focused setup instructions, including a direnv/nix-direnv workflow and a manual nix develop alternative.
• Chores
  • Updated project environment and ignore settings to improve flake/direnv usability and ignore local editor/cache files.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 50337665-ac94-4a5d-a4b5-65a4b49b80d9

📥 Commits

Reviewing files that changed from the base of the PR and between 6b4a133 and f9ebaa0.

📒 Files selected for processing (1)

• README.md

✅ Files skipped from review due to trivial changes (1)

• README.md

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📝 Walkthrough

Walkthrough

Adds Nix flake support for NixOS users. A new flake.nix defines a dev shell with nodejs and electron, setting ELECTRON_EXEC_PATH to the Nix-provided binary. .envrc activates the flake via direnv, .gitignore excludes .cursorrules and .direnv, and README.md documents the Nix setup workflow.

Changes

Nix Flake Development Environment

Layer / File(s)	Summary
Flake definition and direnv integration flake.nix, .envrc, .gitignore	flake.nix defines a default devShell for x86_64-linux and aarch64-linux with nodejs and electron, setting ELECTRON_EXEC_PATH to the Nix electron binary. .envrc adds use flake . to activate via direnv. .gitignore excludes .cursorrules and .direnv.
NixOS setup documentation README.md	Adds a "Using Nix" subsection to Project Setup covering direnv/nix-direnv activation, manual nix develop workflow, and documentation that ELECTRON_EXEC_PATH from the flake eliminates the need for LD_LIBRARY_PATH exports.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐇 A flake upon the shelf today,
Nix shells for those on NixOS way.
use flake . — direnv agrees,
Electron found with greatest ease.
No LD_LIBRARY_PATH to fuss,
The rabbit hops without a fuss! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: add Nix flake dev environment' accurately captures the main change: adding a Nix flake configuration for a development environment, which is the core of the PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@README.md`:
- Around line 11-30: The README.md documentation at line 29 references an
incorrect environment variable name `ELECTRON_OVERRIDE_DIST_PATH`, but the
actual flake.nix implementation sets `ELECTRON_EXEC_PATH`. Update the README.md
to replace the environment variable reference from `ELECTRON_OVERRIDE_DIST_PATH`
to `ELECTRON_EXEC_PATH` to match the actual implementation and keep the
documentation accurate with how electron-vite reads this variable.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 90127b66-ddde-4cd9-8d01-98380da145e4

📥 Commits

Reviewing files that changed from the base of the PR and between d176e7d and 6b4a133.

⛔ Files ignored due to path filters (1)

• flake.lock is excluded by !**/*.lock

📒 Files selected for processing (4)

• .envrc
• .gitignore
• README.md
• flake.nix