Replace stub implementations with real esptool subprocess calls.
Each operation runs esptool as an async subprocess with timeout,
matching the chip_control pattern. All four tools now work with
both physical ports and QEMU socket:// URIs.
Port allocator was counting stopped QEMU instances as occupying ports,
preventing new starts after stop-all. Only running instances now block
port reuse. Stopped instances with flash images on disk are preserved
for esp_qemu_flash; truly stale entries are purged.
Sort glob results when auto-detecting QEMU binaries to reliably
pick the newest version. Previously filesystem ordering could select
an older build (8.2.0 instead of 9.0.0), missing ESP32-S3 support.
Remove ESP32-S2 from CHIP_MACHINES — the Espressif QEMU fork has
no esp32s2 machine type.
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.
