Rewrite of cbsdk

[cboulay]

Modular rewrite of cbsdk

Replaces the monolithic cbsdk with a layered architecture:

cbproto → Protocol definitions, packet types, translation between protocol versions
cbshm → Shared memory (Central-compat and native layouts)
cbdev → Device transport (UDP sockets, handshake, clock sync, threaded receive)
cbsdk → SDK orchestration (cbdev + cbshm + typed callbacks + config queries)
ccfutils → CCF XML config file load/save
pycbsdk → Python wrapper via cffi ABI mode (no compiler needed at install)

Key capabilities

• STANDALONE mode: CereLink owns the device connection and shared memory
• CLIENT mode: Attach to another CereLink instance's shared memory
• CENTRAL_COMPAT CLIENT mode: Attach to Central's shared memory with on-the-fly protocol translation
• C API: 30+ exported functions in cbsdk.h with CBSDK_API for DLL export
• Python API: pycbsdk package with decorator-based callbacks (@session.on_event, @session.on_group)
• Protocol translation: Bidirectional translation between protocol versions (3.11 ↔ 4.0 ↔ 4.1 ↔ 4.2)
• Clock sync: Device-to-host time synchronization
• All device types: LEGACY_NSP, NSP, HUB1–HUB3, NPLAY, CUSTOM
• GHA CI: Automated tests (Windows/macOS/Linux) and wheel builds for pycbsdk

Remaining work

• Modular architecture (cbproto, cbshm, cbdev, cbsdk, ccfutils)
• STANDALONE and CLIENT modes
• Central-compat CLIENT mode with protocol translation
• C API with DLL export
• Python wrapper (pycbsdk) with cffi
• Typed callbacks (event, group, config)
• CCF file load/save
• Clock sync
• GHA CI for tests and wheel builds
• Instrument time API (full stack)
• Patient info API (full stack)
• Analog output monitoring API (full stack)
• Central recording control (open/start/stop/close)
• Channel config get/set accessors (C API + Python)
• Protocol version query API
• Spike processing config (spike length, pretrigger)
• Analog output waveform generation
• Matlab bindings
• C# bindings

[cboulay]

Matlab bindings will come later.
This is ready for review and will likely be merged soon!