Deprecate Homebrew tap in favor of Homebrew Core and signed .pkgs (#1347)

* Deprecate Homebrew tap in favor of Homebrew Core and signed `.pkg`s

This tap is broken and unmaintained, and PowerShell is now available
directly from Homebrew Core (`brew install powershell`), so there's no
reason to keep pointing people here.

- Add a prominent deprecation warning at the top of the README
- Document the recommended install paths: the community Homebrew Core
  formula (copied from the updated docs Sean linked) and the macOS
  `.pkg` installers, which are signed and notarized by Microsoft as of
  the May 2026 releases and are therefore a fully supported path
- Remove the old `powershell/tap/*` install instructions since those
  formulas no longer work

Closes #1342.

Drafted by Copilot (Claude Opus 4.8).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* List the official signed `.pkg` installer as the primary macOS path

Reorder the recommended installation methods so the official, signed and
notarized `.pkg` installers published by the PowerShell project come first,
ahead of the community Homebrew Core formula. The `.pkg` packages are
Microsoft-built and supported, so they're the better default recommendation,
with Homebrew (which builds from source and is community-supported) as the
alternative.

Drafted by Copilot (Claude Opus 4.8).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Link the PowerShell project and drop Gatekeeper notes

- Link references to the PowerShell project to its repository at
  https://github.com/PowerShell/PowerShell
- Remove the Gatekeeper workaround mentions, since the signed and notarized
  `.pkg` packages no longer require bypassing Gatekeeper and we don't want to
  document the old workarounds here

Drafted by Copilot (Claude Opus 4.8).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andyleejordan

README.md

@@ -1,83 +1,79 @@
 # Homebrew tap for PowerShell Products
 
-## Requirements
-
-1. You must be running a version of macOS supported by PowerShell.
-1. See [Homebrew requirements](https://docs.brew.sh/Installation#macos-requirements)
-
-## Fomula List
+> [!WARNING]
+> **This tap is deprecated and no longer maintained.**
+>
+> PowerShell is now available directly from the official, signed and notarized
+> `.pkg` installers published by the [PowerShell project](https://github.com/PowerShell/PowerShell),
+> as well as from
+> [Homebrew Core](https://formulae.brew.sh/formula/powershell). Please migrate to
+> one of the [recommended installation methods](#recommended-installation) below.
+> The `powershell/tap/*` formulas in this repository no longer work.
 
-### PowerShell Channels
+## Recommended installation
 
-* [Stable](#powershell-stable)
-* [Preview](#powershell-preview)
-* [LTS](#powershell-lts)
-* [~~Daily~~](#powershell-daily)
-  * Daily is marked as not supported and will only be occasionally update. 
-    Please move to one of the other channels.
-    
-Learn more about using PowerShell ...
+### Official `.pkg` installer (recommended)
 
-Issues can be reported at [PowerShell/PowerShell](https://github.com/PowerShell/PowerShell/issues/new/choose).
+The [PowerShell project](https://github.com/PowerShell/PowerShell) publishes
+macOS `.pkg` installers for both Apple silicon (`arm64`) and Intel (`x64`) Macs.
+Beginning with the May 2026 releases, these packages are **notarized and signed
+by Microsoft**, so you can download and open them directly.
 
-## Install Instructions
+1. Download the `.pkg` for your processor architecture from the
+   [PowerShell releases page](https://github.com/PowerShell/PowerShell/releases).
+2. Double-click the downloaded package and follow the installer prompts.
 
-### PowerShell Stable
-
-```
-brew install powershell/tap/powershell
-```
+To update, download and install the newer package. For full instructions, see
+[Install PowerShell on macOS](https://learn.microsoft.com/powershell/scripting/install/install-powershell-on-macos).
 
-You can now run the `pwsh` to get started.
+### Homebrew (community formula)
 
-To upgrade to the latest version, run:
+PowerShell is also published to [Homebrew Core](https://formulae.brew.sh/formula/powershell),
+so you no longer need this tap. Install it with:
 
-```
-brew upgrade powershell
+```sh
+brew install powershell
 ```
 
-### PowerShell Preview
+If you previously installed PowerShell using the Homebrew cask, you must first
+uninstall the cask before you can successfully install using the Homebrew
+formula:
 
+```sh
+# Uninstall the PowerShell cask instance
+brew uninstall --cask powershell
+# Uninstall the PowerShell Preview cask instance
+brew uninstall --cask powershell-preview
 ```
-brew install powershell/tap/powershell-preview
-```
-
-You can now run the `pwsh-preview` to get started.
 
-To upgrade to the latest version, run:
+If you receive the message *"Warning: PowerShell is already installed, it's just
+not linked."*, run:
 
-```
-brew upgrade powershell-preview
+```sh
+brew link powershell
 ```
 
-### PowerShell LTS
+To update PowerShell to the latest release:
 
+```sh
+brew update
+brew upgrade powershell
 ```
-brew install powershell/tap/powershell-lts
-```
-
-You can now run the `pwsh-lts` to get started.
-
-To upgrade to the latest version, run:
-
-```
-brew upgrade powershell-lts
-```
-
 
-### PowerShell Daily
+> [!NOTE]
+> The brew formula is maintained and supported by the Homebrew community. It
+> builds PowerShell from source code rather than installing a package built by
+> Microsoft. See
+> [Alternate ways to install PowerShell](https://learn.microsoft.com/powershell/scripting/install/alternate-install-methods#install-on-macos-using-homebrew)
+> for details.
 
-```
-brew install powershell/tap/powershell-daily
-```
-
-You can now run the `pwsh-daily` to get started.
+## Requirements
 
-To upgrade to the latest version, run:
+1. You must be running a version of macOS supported by PowerShell.
+1. See [Homebrew requirements](https://docs.brew.sh/Installation#macos-requirements).
 
-```
-brew upgrade powershell-daily
-```
+Issues with PowerShell itself can be reported at
+[PowerShell/PowerShell](https://github.com/PowerShell/PowerShell/issues/new/choose).
 
 ## Code of Conduct