[Feature]: Restore Homebrew Support for the TWG CLI

## Problem or Opportunity

The `atlassian/twg` Homebrew tap installed the TWG CLI until version 1.0.1.
The tap remote now returns an error:

```text
remote: Repository not found.
fatal: repository 'https://github.com/atlassian/homebrew-twg/' not found
```

Homebrew cannot fetch the tap, so the local formula stays at version 1.0.1.
The `brew upgrade twg` command cannot install a later release.

Version 1.0.1 of the CLI tells the user to run that command:

```text
Update available: 1.0.1 -> 1.1.1. Run 'brew upgrade twg' or visit
https://teamwork-graph.atlassian.com/cli/install
```

The Homebrew archive for version 1.1.1 also returns HTTP 404:

```text
https://teamwork-graph.atlassian.com/cli/homebrew/1.1.1/twg-1.1.1-darwin-arm64.tar.gz
```

The archive for version 1.0.1 at the equivalent path still resolves.
The `atlassian/homebrew-tap` repository holds only Atlassian Plugin SDK
formulae and contains no TWG CLI formula.

The public README and the `docs/` directory contain no Homebrew reference.
The installer script at `/cli/install` contains no Homebrew reference.

Homebrew users therefore receive an upgrade instruction that cannot succeed,
and they receive no message about the change of install method.

## Proposed Outcome

1. Restore Homebrew as a supported install and update channel.
2. Publish the formula in a tap that Atlassian maintains and documents.
3. Publish a Homebrew archive and checksum for each public release.
4. State the Homebrew install command in the public README.

If Atlassian retires Homebrew support, please deliver these outcomes instead:

1. Detect a Homebrew installation and print the correct update command.
2. Record the removal of Homebrew support in `CHANGELOG.md`.
3. Publish a short migration procedure for existing Homebrew users.

## Area

Install, update, or setup

## Current Workaround

Run the installer script, which writes the binary to `~/.local/bin`:

```shell
bash <(curl -fsSL https://teamwork-graph.atlassian.com/cli/install)
```

Then remove the Homebrew installation and the dead tap:

```shell
brew uninstall twg
brew untap atlassian/twg
```

## Environment

| Item | Value |
| --- | --- |
| Installed version | 1.0.1 (beta) |
| Latest version | 1.1.1 |
| Install method | Homebrew, tap `atlassian/twg` |
| Homebrew version | 6.0.17 |
| Platform | macOS 26.3.2, arm64 |

Start by reading the public README, docs/, the installer entry point at /cli/install, and CHANGELOG.md, then verify the current tap, formula, archive, and checksum URLs from the issue. The issue presents both restoring Homebrew and retiring it as possible outcomes, so confirm that direction with maintainers before defining completion.

Written by the indexing model from the issue text.