Add ESP32 support with secureLSL encryption

[neuromechanist]

Summary

Adds liblsl-ESP32: a clean-room C reimplementation of the LSL wire protocol for ESP32 microcontrollers with full secureLSL encryption support.

What's included

Core library (liblsl-ESP32/components/liblsl_esp32/, ~4100 lines C)

• LSL protocol v1.10: UDP multicast discovery + TCP data streaming
• Bidirectional: outlet (push) and inlet (pull)
• secureLSL encryption: ChaCha20-Poly1305, Ed25519, wire-compatible with desktop
• Pre-allocated memory architecture (~200KB SRAM, 300KB+ free for application)

Examples (4 projects)

• basic_outlet, basic_inlet (unencrypted)
• secure_outlet, secure_inlet (encrypted, with key provisioning via menuconfig)

Benchmarks (firmware + desktop Python scripts)

• Throughput benchmark: configurable channels, rate, security
• Desktop collection scripts for jitter/throughput/loss measurement

Documentation (integrated into mkdocs)

• docs/esp32/overview.md -- scope, quick start, API, performance, compatibility
• liblsl-ESP32/docs/ -- architecture, security guide, benchmarks

Key design decisions

• Clean reimplementation (not a port): desktop liblsl's Boost/C++ stack is impractical on 520KB SRAM
• Communication layer only: designed to pair with dedicated ADC ICs for biosignal acquisition
• Transport-agnostic: WiFi current, extensible to Ethernet/Bluetooth/ESP-NOW
• Low-latency local network scope (consistent with LSL design)

Hardware-verified performance

Config	Rate	Loss	Encryption overhead
8ch float32	250 Hz	0%	Not measurable (async)
8ch float32	1000 Hz	0.02%	Not measurable (async)
64ch float32	250 Hz	0%	Not measurable (async)

Bidirectional encrypted interop verified with desktop secureLSL (cpp_secure_inlet/outlet).

Protocol compatibility

Feature	Desktop liblsl	liblsl-ESP32
Protocol	1.00 + 1.10	1.10 only
IP	IPv4 + IPv6	IPv4 only
Formats	All	float32, double64, int32, int16, int8
secureLSL	Yes	Yes (wire-compatible)
Max connections	Unlimited	3
Max channels	Unlimited	128

[neuromechanist]

PR Review Complete - All findings addressed

Code reviewer (5 findings)

#	Finding	Fix
1	Missing copyright on 21 files	Added to all wifi_helpers, crypto_bench, build_test
2	sodium_init doc inconsistency	Updated: "initializes internally if needed"
3	export_pubkey loads secret key	Noted for future optimization (not blocking)
4	Nonce policy difference vs desktop	Documented with comment in security_decrypt
5	Stack allocation in resolve_streams	Verified safe for current MAX_RESULTS

Doc reviewer (13 findings)

#	Finding	Fix
1	"Ed25519 key exchange" incorrect	Changed to "X25519 key exchange (from Ed25519 identity)"
2	private_key vs encrypted_private_key	Added !!! note caveat about ESP32 raw key storage
3	Missing key distribution step	Reordered: import desktop keys as recommended workflow
4	Key extraction snippet fragile	Removed from overview, linked to security guide
5	"Not measurable" misleading	Changed to "2 KB heap (push async)"
6	Missing MkDocs admonitions/separators	Added !!! warning, !!! note, --- separators
7	Inconsistent product name	Standardized within page
8	Missing API functions in overview	Added export_pubkey, has_keypair
9	Broken relative links	Changed to GitHub URLs
10	Documentation links broken on mkdocs	Changed to GitHub URLs
11	Missing Installation cross-reference	Added link to getting-started/installation
12	Inconsistent line count	Standardized to ~4,000
13	Duplicated key extraction snippet	Removed, linked to security guide

Positive findings

• Scope section well-written and scientifically grounded
• Protocol compatibility table honest about limitations
• Wire format verified correct against desktop secureLSL
• No hardcoded credentials in codebase
• Memory safety thorough with bounds checking throughout