Ship a Homebrew tap for the thinkrail CLI and desktop cask

## Problem

Today the only macOS install paths are `curl ... | bash`. Piping a remote script into a shell is a habit many developers avoid, and it sits outside the tooling that already manages the rest of their machine: Homebrew tracks what is installed, upgrades everything in one `brew upgrade`, and integrates with provisioning tools like Ansible's `homebrew` module and `Brewfile`s.

## Proposed solution

Publish an official tap, e.g. `JetBrains/homebrew-thinkrail`, with:

- a `thinkrail` **formula** that downloads the release binary for the platform (`darwin-arm64`, `darwin-x64`, `linux-x64`, `linux-arm64`) and verifies the `SHA256SUMS` already published per release;
- a `thinkrail` **cask** for the Electrobun desktop app, so `brew install --cask thinkrail` works too.

Both should be bumped automatically from the release workflow, so the tap never lags behind.

With a tap in place the README can offer:

```sh
brew install JetBrains/thinkrail/thinkrail
brew install --cask JetBrains/thinkrail/thinkrail
```

A nightly channel could be a second formula (`thinkrail@nightly`) if wanted.

## Alternatives considered

- Publishing to Homebrew cask core.
- `bun install -g` from npm.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Start by inspecting the release workflow, the published platform binaries, and each release's SHA256SUMS. Define the tap's thinkrail formula and Electrobun cask, then update the README with the proposed brew commands. Done means both install paths work for the listed platforms and the tap is bumped automatically from releases.

Written by the indexing model from the issue text.