Reorganize: Move all skills to skills/ folder

- Created skills/ directory
- Moved 272 skills to skills/ subfolder
- Kept agents/ at root level
- Kept installation scripts and docs at root level

Repository structure:
- skills/           - All 272 skills from skills.sh
- agents/           - Agent definitions
- *.sh, *.ps1       - Installation scripts
- README.md, etc.   - Documentation

Co-Authored-By: Claude <noreply@anthropic.com>

skills/swift-concurrency-expert/skill.md

@@ -0,0 +1,37 @@
+---
+name: swift-concurrency-expert
+description: Swift Concurrency review and remediation for Swift 6.2+. Use when asked to review Swift Concurrency usage, improve concurrency compliance, or fix Swift concurrency compiler errors in a feature or file.
+---
+
+# Swift Concurrency Expert
+
+## Overview
+
+Review and fix Swift Concurrency issues in Swift 6.2+ codebases by applying actor isolation, Sendable safety, and modern concurrency patterns with minimal behavior changes.
+
+## Workflow
+
+### 1. Triage the issue
+
+- Capture the exact compiler diagnostics and the offending symbol(s).
+- Check project concurrency settings: Swift language version (6.2+), strict concurrency level, and whether approachable concurrency (default actor isolation / main-actor-by-default) is enabled.
+- Identify the current actor context (`@MainActor`, `actor`, `nonisolated`) and whether a default actor isolation mode is enabled.
+- Confirm whether the code is UI-bound or intended to run off the main actor.
+
+### 2. Apply the smallest safe fix
+
+Prefer edits that preserve existing behavior while satisfying data-race safety.
+
+Common fixes:
+- **UI-bound types**: annotate the type or relevant members with `@MainActor`.
+- **Protocol conformance on main actor types**: make the conformance isolated (e.g., `extension Foo: @MainActor SomeProtocol`).
+- **Global/static state**: protect with `@MainActor` or move into an actor.
+- **Background work**: move expensive work into a `@concurrent` async function on a `nonisolated` type or use an `actor` to guard mutable state.
+- **Sendable errors**: prefer immutable/value types; add `Sendable` conformance only when correct; avoid `@unchecked Sendable` unless you can prove thread safety.
+
+
+## Reference material
+
+- See `references/swift-6-2-concurrency.md` for Swift 6.2 changes, patterns, and examples.
+- See `references/approachable-concurrency.md` when the project is opted into approachable concurrency mode.
+- See `references/swiftui-concurrency-tour-wwdc.md` for SwiftUI-specific concurrency guidance.