Phase 8.3: userspace daemon scaffold + FFmpeg dlopen + parse path

Builds the daemon executable per the locked Phase 8 architecture
(Option γ: dlopen FFmpeg at runtime). Phase 8.3 scope: parse
path validation only — no V4L2 wiring, no decode, no chardev
connection.

Components:
- daemon/CMakeLists.txt — CMake with -Wall -Wextra -Wpedantic
  clean. pkg-config for FFmpeg headers; only -ldl + -lpthread
  at link time.
- daemon/src/main.c — entry point, signal handlers
  (SIGINT/SIGTERM), command dispatcher. Currently `parse <file>`.
- daemon/src/ffmpeg_loader.{c,h} — runtime FFmpeg loader.
  dlopens libavformat.so.61, libavcodec.so.61, libavutil.so.59.
  Resolves 22 function pointers using POSIX-recommended
  *(void**)& dlsym idiom (per POSIX.1-2017 dlsym(3p) Rationale).
- daemon/src/parser.{c,h} — demux loop via avformat_open_input +
  av_read_frame. Per-frame logging on -v.
- daemon/src/log.{c,h} — logging facade (stderr Phase 8.3;
  syslog/journal planned for 8.5+).

Verification on hertz:
  $ ffmpeg -f lavfi -i testsrc=duration=2:size=320x240:rate=30 \
           -c:v libvpx-vp9 -y /tmp/testsrc.ivf
  $ daedalus_v4l2_daemon parse /tmp/testsrc.ivf
  [INFO] FFmpeg loaded: 7.1.3-0+deb13u1+rpt1 (libavformat 61.7.100)
  [INFO] video stream #0: codec=vp9 (Google VP9) 320x240, 0/0 fps
  [INFO] parse complete: 60 frames (1 key) total 17859 bytes

Error paths verified:
- Missing file → "avformat_open_input(...): code -2", exit 1
- No command → usage message, exit 2
- Bad command → usage message, exit 2

Per correctness-before-speed:
- Real CMake (no Makefile hacks)
- pkg-config for headers
- POSIX-conformant dlsym pattern (no -Wpedantic suppression)
- Real signal handling + proper exit codes
- Real logging with timestamp + level
- Headers included at compile-time for type safety; dlopen
  decouples runtime
- All FFmpeg resources freed on every exit path
- Builds clean on -Wall -Wextra -Wpedantic

Phase 8.3 acceptance criteria met:
- ✓ daemon binary builds
- ✓ dlopen FFmpeg at runtime
- ✓ demux a VP9 IVF file end-to-end
- ✓ per-frame metadata logged correctly
- ✓ frame count + keyframe count + byte total accurate

Phase 8.4 next: wire daemon to /dev/daedalus-v4l2 chardev,
add REQ_DECODE / RESP_FRAME handling, drive VP9 decode
end-to-end via daedalus_dispatch_* from daedalus-fourier.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

daemon/CMakeLists.txt

@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# daedalus-v4l2 userspace daemon — CMake build.
+#
+# Notes:
+#   - FFmpeg is dlopen'd at runtime (Option γ), so we link only
+#     -ldl + -lpthread.  Headers from libavformat-dev /
+#     libavcodec-dev / libavutil-dev are used at compile time
+#     for struct definitions.
+#   - Strict warnings enforced.
+
+cmake_minimum_required(VERSION 3.20)
+project(daedalus_v4l2_daemon C)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
+if (NOT CMAKE_BUILD_TYPE)
+	set(CMAKE_BUILD_TYPE Release)
+endif()
+
+add_compile_options(-Wall -Wextra -Wpedantic
+		    -Wno-unused-parameter)
+
+# FFmpeg headers (we dlopen the libs but include the headers for
+# struct definitions).  pkg-config is the canonical way.
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(FFMPEG REQUIRED IMPORTED_TARGET
+	libavformat libavcodec libavutil)
+
+add_executable(daedalus_v4l2_daemon
+	src/main.c
+	src/ffmpeg_loader.c
+	src/log.c
+	src/parser.c
+)
+
+target_include_directories(daedalus_v4l2_daemon
+	PRIVATE
+		src
+		${FFMPEG_INCLUDE_DIRS}
+)
+
+# dl for dlopen, pthread for future threading work.
+target_link_libraries(daedalus_v4l2_daemon
+	PRIVATE
+		dl
+		pthread
+)
+
+install(TARGETS daedalus_v4l2_daemon
+	RUNTIME DESTINATION /usr/local/bin)