AGENTS.md: replace the 'no AI attribution footers' rule with a requirement that every agent-authored/co-authored commit end with a Co-Authored-By trailer naming the specific agent/model. Add docs/SWIFT_GUIDELINES.md to the repo layout.
docs/SWIFT_GUIDELINES.md: consolidate the team Swift standards (coding style, testing, patterns, security, tooling hooks) into a self-contained project doc, with project notes for Xcode MCP, MainActor/Sendable, and SwiftData gotchas.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
