feat: add Waza devcontainer feature

[Copilot]

Adds a new devcontainer feature to install Waza, Microsoft's AI-powered CLI agent for evaluating Agent Skills.

New feature: waza

• features/src/waza/ — Go installer fetches tags from microsoft/waza, downloads the pre-built binary (waza-linux-{amd64,arm64}) directly from GitHub releases (no archive), and installs to /usr/local/bin/waza
• features/src/waza/devcontainer-feature.json — Exposes version (default: latest) and downloadUrl options for corporate artifact proxy support
• features/test/waza/ — Scenario test pinned to 0.38.5 on Debian 12/13 and Ubuntu 24.04/26.04

Supporting changes

• build/build.go — Registers Feature:waza:Package and Feature:waza:Test tasks
• override-all.env — Adds WAZA_DOWNLOAD_URL override variable

Usage

"features": {
  "ghcr.io/postfinance/devcontainer-features/waza:1": {
    "version": "latest"
  }
}

• Fixes Create a feature that installs waza (https://github.com/microsoft/waza) #68

[Roemer]

• There is a binary added, remove it
• Add it to the ci
• Add the environmen variable WAZA_NO_UPDATE_CHECK=1 to the devcontainer-feature.json