Improve BLE transfer diagnostics for compressed header (0x0002) detection

[Copilot]

RELATED TO: martinberlin/FastJsonRenderer#15
Compressed BLE transfers were still failing while uncompressed (0x0001) payloads arrived and rendered correctly, making it unclear whether the sender was emitting the expected compressed header. This change adds targeted logging to make header-type mismatches immediately visible at receive time.

• Header decode observability

  • Log the first two header bytes and decoded uint16 type on first chunk parse.
  • Makes endianness and sender framing errors obvious from a single log line.

• Explicit compressed-path signal

  • Add a dedicated log when HEADER_TYPE_DEFLATE (0x0002) is detected.
  • Removes ambiguity when comparing compressed vs uncompressed sessions.

• More actionable fallback warning

  • When header parsing fails, include the decoded type in the headerless-mode warning.
  • Helps distinguish “missing header” from “wrong header value”.

ESP_LOGI(TAG, "Header bytes: [%02x %02x] decoded type=0x%04x",
         param->write.value[0], param->write.value[1], hdr_type);

if (hdr_type == HEADER_TYPE_DEFLATE) {
    ESP_LOGI(TAG, "Compressed header detected (0x0002)");
}

[martinberlin]

Working as expected