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/security-scanning/skills/attack-tree-construction/SKILL.md

@@ -679,9 +679,3 @@ class AttackPathAnalyzer:
 - **Don't forget insider threats** - Not all attackers are external
 - **Don't skip mitigations** - Trees are for defense planning
 - **Don't make it static** - Threat landscape evolves
-
-## Resources
-
-- [Attack Trees by Bruce Schneier](https://www.schneier.com/academic/archives/1999/12/attack_trees.html)
-- [MITRE ATT&CK Framework](https://attack.mitre.org/)
-- [OWASP Attack Surface Analysis](https://owasp.org/www-community/controls/Attack_Surface_Analysis_Cheat_Sheet)

plugins/security-scanning/skills/security-requirement-extraction/SKILL.md

@@ -671,9 +671,3 @@ This epic covers all security requirements related to {domain.value.replace('_',
 - **Don't ignore priorities** - Not all requirements are equal
 - **Don't forget testability** - If you can't test it, you can't verify it
 - **Don't work in isolation** - Involve stakeholders
-
-## Resources
-
-- [OWASP ASVS](https://owasp.org/www-project-application-security-verification-standard/)
-- [NIST SP 800-53](https://csrc.nist.gov/publications/detail/sp/800-53/rev-5/final)
-- [Security User Stories](https://www.oreilly.com/library/view/agile-application-security/9781491938836/)

plugins/security-scanning/skills/stride-analysis-patterns/SKILL.md

@@ -656,9 +656,3 @@ class StridePerInteraction:
 - **Don't work in isolation** - Collaborative modeling is better
 - **Don't ignore low-probability** - High-impact threats matter
 - **Don't stop at identification** - Follow through with mitigations
-
-## Resources
-
-- [Microsoft STRIDE Documentation](https://docs.microsoft.com/en-us/azure/security/develop/threat-modeling-tool-threats)
-- [OWASP Threat Modeling](https://owasp.org/www-community/Threat_Modeling)
-- [Threat Modeling: Designing for Security](https://www.wiley.com/en-us/Threat+Modeling%3A+Designing+for+Security-p-9781118809990)

plugins/security-scanning/skills/threat-mitigation-mapping/SKILL.md

@@ -739,9 +739,3 @@ class ControlTester:
 - **Don't skip testing** - Untested controls may fail
 - **Don't set and forget** - Continuous improvement
 - **Don't ignore people/process** - Technology alone isn't enough
-
-## Resources
-
-- [NIST Cybersecurity Framework](https://www.nist.gov/cyberframework)
-- [CIS Controls](https://www.cisecurity.org/controls)
-- [MITRE D3FEND](https://d3fend.mitre.org/)