Add async-profiler skill for Java profiling 🤖🤖🤖

[vetler]

What this adds

A skill for installing, running, and analyzing async-profiler for Java — a low-overhead sampling profiler that produces flamegraphs, JFR recordings, and allocation profiles.

Why it's useful

async-profiler is a niche, specialized tool with platform-specific quirks that frontier models don't reliably handle:

• Exact asprof CLI flags and syntax
• macOS-specific limitations (itimer vs perf_events, asprof stop -f output-path bug)
• JVM flags required for accurate profiles (-XX:+UnlockDiagnosticVMOptions -XX:+DebugNonSafepoints)
• Specific version/download URLs
• How to interpret flamegraph patterns (GC pressure, N+1 Hibernate, lock contention)

Structure

skills/async-profiler/
├── SKILL.md                      # Entry point — routes to focused guides
├── README.md                     # Human-readable overview
├── references/
│   ├── setup.md                  # Installation and configuration
│   ├── profile.md                # Running profiling sessions
│   └── analyze.md                # Interpreting profiling output
└── scripts/
    ├── install.sh                # Platform auto-detect installer
    ├── run_profile.sh            # asprof wrapper with timestamped output
    ├── collect.sh                # Background start/stop collection
    └── analyze_collapsed.py      # Ranked self-time table for .collapsed files

Validation

• npm run skill:validate ✅
• npm run build ✅