libcuframes v0.1: producer + consumer (sync + async) + tests

Implements Steps 3-6 of Phase 1 according to docs/protocol.md.

libcuframes/src/:
- internal.h     (660 lines) — shared structs (byte-exact protocol.md layout)
                                + _Static_assert на offsets/sizes
- utils.c        — error strings, frame size calc, now_ns, key validation
- protocol.c     — TLV framing для Unix socket с poll-based timeout
- producer.c     (~700 lines) — Step 3:
                    * LIBRARY mode: cudaMalloc pool, IPC handle export
                    * EXTERNAL mode: register user-provided pointers
                    * cudaIpcEventHandle_t для cross-process sync (R1/R2)
                    * Unix socket accept thread, handshake state machine
                    * Bit allocation 1..31, name collision check (Y5)
                    * STRICT_WAIT policy: timeout with dead-subscriber eviction
- consumer.c     (~400 lines) — Step 4:
                    * Synchronous next() with poll-based wait
                    * cudaStreamWaitEvent на consumer-stream (R1/R2)
                    * Opaque cuframes_frame_t с accessor functions (Y6)
                    * NEWEST_ONLY и STRICT_ORDER modes
                    * ACK via atomic_fetch_or на bitmap
- consumer_async.c — Step 5: thread + callback wrapper над sync API

libcuframes/tests/:
- test_pingpong.cu — single producer × single consumer, 200 frames @ 60fps,
                     verify через kernel-on-consumer-stream (правильный test
                     для sync semantics, см. spike-v2)
- test_multi.cu    — 1 producer × 3 consumers через fork()

Build:
- Top-level CMakeLists.txt с options
- libcuframes/CMakeLists.txt: shared + static library, c_std_11
- Suppress -Waddress-of-packed-member (известная безопасная warning x86_64)

Results (внутри cuframes-dev container, RTX 5090):
- pingpong_basic PASS  4.5s  200 frames, 0 torn
- multi_consumer PASS  4.1s  1 × 3 consumers, all PASS

Phase 1 Step 6 done. Дальше: Step 7 (C++ wrapper), Step 9 (FFmpeg filter).

CMakeLists.txt

@@ -0,0 +1,32 @@
+cmake_minimum_required(VERSION 3.20)
+project(cuframes
+    VERSION 0.1.0
+    DESCRIPTION "Zero-copy frame sharing via CUDA IPC"
+    LANGUAGES C CXX CUDA
+)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+if(NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE Release)
+endif()
+
+if(NOT DEFINED CMAKE_CUDA_ARCHITECTURES)
+    set(CMAKE_CUDA_ARCHITECTURES "75;86;89;90;120")
+endif()
+
+option(BUILD_TESTING "Build tests" ON)
+option(BUILD_EXAMPLES "Build examples" ON)
+option(BUILD_FFMPEG_FILTER "Build FFmpeg vf_cuda_ipc_export filter" OFF)
+option(BUILD_PYTHON_BINDINGS "Build Python bindings" OFF)
+
+enable_testing()
+
+add_subdirectory(libcuframes)
+
+if(BUILD_FFMPEG_FILTER)
+    add_subdirectory(filter)
+endif()