[AFL++] Crash management and local reproduction tooling

[vyavdoshenko]

Scope

• Collect stacktraces, build info (commit, flags), and environment.
• Provide tools/fuzz/repro.sh to reproduce any crash artifact locally.
• Prepare an auto-issue template for crashes with minimized input attached.

Tasks

• Implement standardized artifact bundle format (input, logs, meta.json).
• Implement a repro script that runs the exact target/flags on the artifact.
• Add an ISSUE_TEMPLATE for fuzz crashes.