BetaCalendarsKit 1.0.0

First stable release of BetaCalendarsKit.

• Gregorian civil-day values and explicit calendar contexts.
• Compact and fixed six-week month/year grid generation.
• Bounded weekly, monthly, annual, and interval recurrence with explicit missing-date policies.
• Structured calendar and time-zone boundary analysis.
• Deterministic Codable fixtures and the betacal command-line tool.
• DocC guides for Core, Recurrence, and Fixtures.

Built with Swift 6 strict concurrency checks. See README and CHANGELOG.