feat: publish Chocolatey package for Windows installation

[IceRhymers]

Goal

Allow Windows users to install via: choco install databricks-claude

How Chocolatey works

Chocolatey packages are NuGet packages containing a .nuspec and PowerShell install scripts, published to the Chocolatey Community Repository.

What to add

• chocolatey/databricks-claude.nuspec — package metadata (id, version, authors, description, MIT license, projectUrl, tags)
• chocolatey/tools/chocolateyInstall.ps1 — downloads the windows-amd64 .exe from GitHub releases, verifies SHA256 checksum, installs to Chocolatey bin path
• chocolatey/tools/chocolateyUninstall.ps1 — cleanup script
• Automate via CI: add a publish-chocolatey job to release.yml that runs choco push using CHOCOLATEY_API_KEY secret
• Add Chocolatey install instructions to README:

  choco install databricks-claude
  

Acceptance Criteria

• choco install databricks-claude works on Windows 10/11
• Package published to community.chocolatey.org
• SHA256 verified during install
• New releases automatically publish updated package via CI