Add basecamp-fizzy-cli feature

[Copilot]

Adds a new devcontainer feature that installs the fizzy CLI — Basecamp's terminal interface for Fizzy project management, designed for both direct use and AI agent integration.

Changes

• src/basecamp-fizzy-cli/devcontainer-feature.json — feature metadata; exposes a version option (default: latest)
• src/basecamp-fizzy-cli/install.sh — downloads the pre-compiled fizzy-linux-{amd64,arm64} binary from GitHub releases to /usr/local/bin/fizzy; resolves latest via GitHub API
• src/basecamp-fizzy-cli/NOTES.md — upstream link, description, and installation notes
• test/basecamp-fizzy-cli/test.sh — verifies fizzy --version exits successfully

Notes

Unlike most other features in this repo, fizzy-cli ships raw binaries (no tarball), so the install script uses a direct curl download rather than curl | tar. Architecture mapping uses Debian names directly (amd64/arm64) since that matches the release asset naming convention.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add basecamp-fizzy-cli feature</issue_title>
<issue_description>Files:

src/(FeatureName)/devcontainer-feature.json
src/(FeatureName)/NOTES.md
src/(FeatureName)/install.sh (make sure to set executable bit)
test/(FeatureName)/test.sh
.github/workflows/test.yaml

Releases:

https://github.com/basecamp/fizzy-cli/releases

Test the installation process extensively before submitting
Watch for files in releases, naming structure, etc.
Test CLI output extensively before writing the test file.

For NOTES.md:
Link to the project that is installed by the feature
Short description of what it does
Installation method
Other notes</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add basecamp-fizzy-cli feature #158

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