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/solidity-security/SKILL.md

@@ -494,32 +494,3 @@ contract WellDocumentedContract {
     }
 }
 ```
-
-## Resources
-
-- **references/reentrancy.md**: Comprehensive reentrancy prevention
-- **references/access-control.md**: Role-based access patterns
-- **references/overflow-underflow.md**: SafeMath and integer safety
-- **references/gas-optimization.md**: Gas saving techniques
-- **references/vulnerability-patterns.md**: Common vulnerability catalog
-- **assets/solidity-contracts-templates.sol**: Secure contract templates
-- **assets/security-checklist.md**: Pre-audit checklist
-- **scripts/analyze-contract.sh**: Static analysis tools
-
-## Tools for Security Analysis
-
-- **Slither**: Static analysis tool
-- **Mythril**: Security analysis tool
-- **Echidna**: Fuzzing tool
-- **Manticore**: Symbolic execution
-- **Securify**: Automated security scanner
-
-## Common Pitfalls
-
-1. **Using `tx.origin` for Authentication**: Use `msg.sender` instead
-2. **Unchecked External Calls**: Always check return values
-3. **Delegatecall to Untrusted Contracts**: Can hijack your contract
-4. **Floating Pragma**: Pin to specific Solidity version
-5. **Missing Events**: Emit events for state changes
-6. **Excessive Gas in Loops**: Can hit block gas limit
-7. **No Upgrade Path**: Consider proxy patterns if upgrades needed