fix(skills): remove phantom resource references and fix CoC links (#447)

Remove references to non-existent resource files (references/, assets/,
scripts/, examples/) from 115 skill SKILL.md files. These sections
pointed to directories and files that were never created, causing
confusion when users install skills.

Also fix broken Code of Conduct links in issue templates to use
absolute GitHub URLs instead of relative paths that 404.

plugins/blockchain-web3/skills/nft-standards/SKILL.md

@@ -353,31 +353,3 @@ contract OptimizedNFT is ERC721A {
     }
 }
 ```
-
-## Resources
-
-- **references/erc721.md**: ERC-721 specification details
-- **references/erc1155.md**: ERC-1155 multi-token standard
-- **references/metadata-standards.md**: Metadata best practices
-- **references/enumeration.md**: Token enumeration patterns
-- **assets/erc721-contract.sol**: Production ERC-721 template
-- **assets/erc1155-contract.sol**: Production ERC-1155 template
-- **assets/metadata-schema.json**: Standard metadata format
-- **assets/metadata-uploader.py**: IPFS upload utility
-
-## Best Practices
-
-1. **Use OpenZeppelin**: Battle-tested implementations
-2. **Pin Metadata**: Use IPFS with pinning service
-3. **Implement Royalties**: EIP-2981 for marketplace compatibility
-4. **Gas Optimization**: Use ERC721A for batch minting
-5. **Reveal Mechanism**: Placeholder → reveal pattern
-6. **Enumeration**: Support walletOfOwner for marketplaces
-7. **Whitelist**: Merkle trees for efficient whitelisting
-
-## Marketplace Integration
-
-- OpenSea: ERC-721/1155, metadata standards
-- LooksRare: Royalty enforcement
-- Rarible: Protocol fees, lazy minting
-- Blur: Gas-optimized trading