Add and update AI coding skills (#8246)

* skill added for RNN android and iOS (#8238)

* skill added for RNN android and iOS

* update for Skills and added to multiple agent folders

* fixing relative path for github copilot

* Add skill document for RN version upgrade process

Formalises the process of adding new React Native version support,
validated against PRs for RN 0.80 through 0.84. Covers CI setup,
dependency analysis, native compilation fixes, and 10 common pitfalls.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Update RN upgrade skill: prefer __has_include and RCT_REMOVE_LEGACY_ARCH

Learned from PR #8244's approach to iOS arch guards:
- Use __has_include for conditional imports (forward-compatible)
- Use #ifndef RCT_REMOVE_LEGACY_ARCH for legacy code blocks (RN 0.84+)
- Added "Research Before Fixing" phase: investigate better approaches
  from the target RN version before pattern-matching on existing code
- Updated all fix patterns and pitfalls to reflect these techniques

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: mark.dev <50657916+markdevocht@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people