Copy C++ emotiv-lsl implementation into src/emotiv/ and integrate with CMake

[Copilot]

Ports the C++ implementation from PhoPersonalOrg/emotiv-lsl@af6294d into this dedicated repo, placing it under src/emotiv/ and wiring it into the existing CMake build system alongside the LSL template targets.

New: src/emotiv/

File	Role
config.h	EEG (128 Hz) and motion (16 Hz) sampling rate constants
emotiv_base.h/cpp	Abstract base: USB HID enumeration, AES-ECB decryption, LSL outlet creation, main streaming loop
emotiv_epoc_x.h/cpp	EPOC X concrete class: serial-number-derived crypto key, EEG/motion/quality packet decoding, LSL channel metadata
main.cpp	Entry point — instantiates EmotivEpocX and calls main_loop()
CMakeLists.txt	Builds emotiv_lsl; selects correct hidapi backend per platform (winapi/darwin/libusb)

CMakeLists.txt (root)

• Added LANGUAGES C (required for aes.c)
• Hoisted include(FetchContent) to top level
• New EMOTIVLSL_BUILD_EMOTIV option (default ON) gates all Emotiv-specific deps and the subdirectory
• FetchContent for hidapi 0.14.0 and tiny-AES-c (source-only; compiled directly into the target with ECB=1, CBC=0, CTR=0)
• add_subdirectory(src/emotiv) + install rule for emotiv_lsl

# Emotiv-only build — no Qt required
cmake -S . -B build -DLSLTEMPLATE_BUILD_GUI=OFF -DLSLTEMPLATE_BUILD_CLI=OFF
cmake --build build --config Release

README

Updated to reflect this repo's purpose: emotiv-specific title/intro, updated project tree, build prerequisites, configure/build/run instructions for all platforms.

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