docs: documentation and operational runbooks for all load testing tools

[kristopherjturner]

Overview

Write comprehensive documentation and operational runbooks for all load testing tools. Documentation should enable a new user to run their first benchmark in under 30 minutes.

Scope

• docs/getting-started.md — Prerequisites, installation, and first run
• docs/configuration/ — Full configuration reference for all tools
• docs/tools/fio.md, hammerdb.md, iperf.md, stressng.md, vmfleet.md — Per-tool runbooks
• docs/reports/ — How to read and interpret results
• docs/troubleshooting.md — Common failure modes and fixes
• API/module reference (auto-generated from docstrings)

Acceptance Criteria

• Getting started guide results in a successful FIO run for a new user
• All configuration parameters documented with type, default, and description
• Per-tool runbooks include example commands and sample output
• Troubleshooting covers top 10 failure modes observed in testing
• Docs site builds without warnings

Dependencies

• Parent Epic: [Epic] Load Testing Toolkit Full Build-Out #8
• All tool integration issues: feat: FIO storage I/O benchmarking integration #12, feat: HammerDB database load testing integration (TPC-C / TPC-H) #13, feat: iPerf3 network throughput and stress-ng CPU/memory integration #14, feat: VMFleet S2D fleet storage testing integration #15

Priority Note

Priority/medium — documentation is deferred until tool integrations stabilize.