chore: release v4.0.0 - sync 550+ skills and restructure docs

skills/memory-safety-patterns/SKILL.md

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+---
+name: memory-safety-patterns
+description: Implement memory-safe programming with RAII, ownership, smart pointers, and resource management across Rust, C++, and C. Use when writing safe systems code, managing resources, or preventing memory bugs.
+---
+
+# Memory Safety Patterns
+
+Cross-language patterns for memory-safe programming including RAII, ownership, smart pointers, and resource management.
+
+## Use this skill when
+
+- Writing memory-safe systems code
+- Managing resources (files, sockets, memory)
+- Preventing use-after-free and leaks
+- Implementing RAII patterns
+- Choosing between languages for safety
+- Debugging memory issues
+
+## Do not use this skill when
+
+- The task is unrelated to memory safety patterns
+- You need a different domain or tool outside this scope
+
+## Instructions
+
+- Clarify goals, constraints, and required inputs.
+- Apply relevant best practices and validate outcomes.
+- Provide actionable steps and verification.
+- If detailed examples are required, open `resources/implementation-playbook.md`.
+
+## Resources
+
+- `resources/implementation-playbook.md` for detailed patterns and examples.