enhance blind-ssrf-chains with attacker infrastructure provisioning g…

[GangGreenTemperTatum]

…uidance

Summary

• Adds "Attacker Infrastructure for SSRF Proof" section to blind-ssrf-chains skill
• Teaches agents to detect available cloud/hosting CLIs on the shell and ask the user which to use when they need to claim a dangling bucket, serve redirects, or host custom content for SSRF proof
• Includes S3 path-style vs website endpoint caveat (x-amz-website-redirect-location only fires on website endpoint, not REST API)