Add tests for URL normalization and Chrome Web Store ID parsing

[culpen90]

Why

Quartz has important parsing behavior in Sources/Quartz/QuartzApp.swift and Sources/Quartz/QuartzWebExtensionSupport.swift: address/search normalization, localhost handling, file/http/https schemes, and Chrome Web Store extension ID extraction. These are easy to regress because the project currently has no test target.

Where to start

• Package.swift
• Sources/Quartz/QuartzApp.swift
• Sources/Quartz/QuartzWebExtensionSupport.swift
• A new Tests/QuartzTests/ target

Suggested approach

Add a small XCTest target and move the pure parsing logic into testable helpers. Keep UI/AppKit code in place; this issue is about extracting only the pure functions needed for tests.

Useful cases to cover:

• example.com becomes https://example.com.
• localhost and localhost:8080 are treated as hosts.
• plain search text becomes a DuckDuckGo search URL.
• http, https, and file URLs are accepted as URLs.
• valid 32-character Chrome Web Store IDs are accepted.
• malformed Chrome Web Store URLs/IDs are rejected.

Acceptance criteria

• swift test runs a new Quartz test target.
• The parsing helpers remain usable by the app.
• Tests cover both successful and rejected inputs.
• swift build still succeeds.

Testing

• Run swift test.
• Run swift build.