Add QEMU section to README with install instructions and tool reference.
Enrich MCP tool docstrings with workflow context, cross-references to
related tools, and guidance on when to use each tool — these descriptions
are read by the calling LLM to decide tool selection.
Smoke tested against real Espressif QEMU fork — esptool successfully
identifies, reads flash_id, and writes firmware to emulated ESP32 via
socket://localhost:5555. Enriched CHIP_MACHINES with per-chip efuse
data, GPIO strap values, and watchdog timer driver names derived from
ESP-IDF's qemu_ext.py.
