fix: ESP-IDF build on master — negentropy_lib component + merge leftoversHEADmaster

- Create components/negentropy_lib/ wrapping negentropy submodule
  - CMakeLists.txt references submodule sources via relative path
  - OpenSSL SHA-256 compat using mbedTLS for ESP32
  - Enables C++ exceptions + RTTI for negentropy_wrapper.cpp
- Remove esp_littlefs, esp_timer from REQUIRES (transitive via wisp_relay)
- Keep tcp_transport (direct dep of stratum_client.c via esp_transport.h)
- Fix config.c duplicate seed_relays/sync_interval/fallback_interval blocks
- Remove leftover merge conflict marker in tollgate_api.c
- Add MINER_INTEGRATION_PLAN.md with miner integration checklist

idf.py build: PASS (1.3MB, 68% free)
make test-unit: PASS (19 suites, 344+ assertions)

1 files changed, 16 insertions, 0 deletions

diff --git a/components/negentropy_lib/compat/openssl/sha.h b/components/negentropy_lib/compat/openssl/sha.h
new file mode 100644
index 0000000..b0881c1
--- /dev/null
+++ b/components/negentropy_lib/compat/openssl/sha.h
@@ -0,0 +1,16 @@
+#ifndef OPENSSL_SHA_COMPAT_H
+#define OPENSSL_SHA_COMPAT_H
+
+#include "mbedtls/sha256.h"
+#include <stddef.h>
+
+#define SHA256_DIGEST_LENGTH 32
+
+static inline int SHA256_compat(const unsigned char *d, size_t n, unsigned char *md)
+{
+    return mbedtls_sha256(d, n, md, 0);
+}
+
+#define SHA256 SHA256_compat
+
+#endif