Add ESP32 minimal project with crash helper

tutorials/esp32/minimal/README.md

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+# ESP32 minimal crash capture
+
+ESP-IDF already captures the ESP32 equivalent of an ARM HardFault. Use the
+ESP-IDF panic handler and ESP-IDF core dump support instead of replacing the
+low-level exception path.
+
+The panic handler captures the architecture-specific fault frame:
+
+- Xtensa targets: PC, PS, A0..A15, SAR, EXCCAUSE, EXCVADDR, loop registers, and
+  backtrace.
+- RISC-V targets: MEPC, RA, SP, MSTATUS, MCAUSE, MTVAL, MHARTID, GPRs, and
+  backtrace.
+
+Fatal classes include CPU exceptions, interrupt watchdog, task watchdog, cache
+errors, brownout, stack overflow, heap corruption, UBSAN checks, and assertions.
+
+This example enables core dump to flash. No filesystem is involved: ESP-IDF
+writes directly to a raw partition table entry of type `data`, subtype
+`coredump`.
+
+```csv
+coredump, data, coredump,, 128K
+```
+
+At panic time, ESP-IDF serializes the crash state into that raw flash partition.
+On the next boot, the application can read it with the user-mode coredump APIs:
+
+```c
+esp_reset_reason();
+esp_core_dump_get_panic_reason(reason, sizeof(reason));
+esp_core_dump_get_summary(summary);
+esp_core_dump_image_get(&addr, &size);
+esp_core_dump_image_erase();
+```
+
+This example exposes:
+
+- `/api/crash`: JSON metadata: reset reason, panic reason, crashed task, PC, and
+  coredump size.
+- `/api/crash.bin`: raw ESP-IDF coredump image, suitable for offline decoding
+  with the application ELF.
+
+The raw coredump can include task stacks, TCBs, selected memory regions, and
+therefore customer-private data. Production upload must treat it as sensitive
+diagnostic material.
+
+## Wizard integration notes
+
+The Wizard ESP-IDF template should keep its existing `mongoose_init()` /
+`mongoose_poll()` structure and register the crash endpoints as custom API
+handlers. The relevant ESP-IDF pieces from this tutorial are:
+
+```ini
+CONFIG_ESP_COREDUMP_ENABLE_TO_FLASH=y
+CONFIG_ESP_COREDUMP_DATA_FORMAT_ELF=y
+CONFIG_ESP_COREDUMP_MAX_TASKS_NUM=16
+CONFIG_ESP_COREDUMP_STACK_SIZE=2048
+```
+
+The ESP-IDF component needs `espcoredump` and `esp_partition`.
+
+Wizard's current 4 MB OTA partition table leaves `0x10000` bytes after SPIFFS,
+so a 64 KB coredump partition fits without changing the app or SPIFFS sizes.
+The 128 KB partition used by this tutorial requires shrinking SPIFFS or one of
+the app slots.
+
+```csv
+coredump, data, coredump,, 64K
+```
+
+The WiFi code is not materially related to crash capture. Apart from where the
+credentials come from, the differences are retry policy, temporary event handler
+lifetime, WPA2/PMF station config, and whether the password is logged. Wizard
+can keep its existing WiFi code for this feature.