Initial scaffold: daedalus-v4l2 sibling repo

V4L2 stateless decoder for Pi 5, backed by sibling
daedalus-fourier kernel library (VP9 + AV1 CDEF + H.264 video
decode kernels on VideoCore VII compute + ARM NEON).

Architecture locked 2026-05-18 by mfritsche per
daedalus-fourier/docs/phase8_scoping.md:
- Option B: Linux kernel V4L2 shim + userspace daemon (not
  v4l2loopback). Real /dev/videoNN; proper DRM PRIME for
  browser zero-copy.
- Option γ: dlopen FFmpeg at runtime as parser. No vendoring;
  fastest to v1.
- Sibling repo (this repo): V4L2-side work outside of
  daedalus-fourier so kernel-library API stays clean.

Components:
  kernel/ - Linux out-of-tree kernel module (GPLv2; V4L2
    device + chardev bridge to userspace daemon)
  daemon/ - userspace decoder daemon (BSD-2-Clause; links
    libdaedalus_core.a from sibling; dlopens FFmpeg)
  docs/   - architecture + 7-phase roadmap (8.1..8.7)
  include/ - shared headers between kernel and daemon

Roadmap (7 sub-phases, ~1 week each):
  8.1 kernel skeleton (/dev/videoNN with no-op ioctls)
  8.2 chardev bridge (kernel ↔ daemon ping-pong)
  8.3 daemon FFmpeg dlopen + parse path
  8.4 VP9 end-to-end via daedalus_dispatch_*
  8.5 dmabuf / DRM PRIME for zero-copy
  8.6 AV1 + H.264 codec support
  8.7 performance: hit 30fps@1080p (project floor)

No code yet — only README + design docs + directory structure.
First implementation work starts in Phase 8.1 next session.

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

daemon/README.md

@@ -0,0 +1,53 @@
+# daemon/ — daedalus-v4l2 userspace decoder daemon
+
+Userspace daemon that:
+1. Connects to the kernel module's chardev
+2. Receives bitstream + V4L2 control blobs
+3. Parses bitstream via dlopen'd FFmpeg
+4. Dispatches per-block work via `daedalus_dispatch_*`
+   from sibling `daedalus-fourier`
+5. Returns decoded frames to kernel
+
+## Status
+
+Scaffold only. Phase 8.3 not yet started.
+
+## Build dependencies (planned)
+
+- libdaedalus_core.a from sibling daedalus-fourier (static link)
+- FFmpeg dev headers (for AVPacket/AVCodec interface types) +
+  runtime FFmpeg .so (loaded via dlopen)
+- libv4l2 (for V4L2 control struct definitions)
+- pthread
+
+## Build (when implemented)
+
+```sh
+mkdir build && cd build
+cmake .. -DDAEDALUS_FOURIER_DIR=/path/to/daedalus-fourier
+make
+```
+
+## Layout (planned)
+
+- `CMakeLists.txt`
+- `src/main.c` — event loop, chardev connection
+- `src/parser.c` — FFmpeg dlopen wrapper + per-codec dispatch
+- `src/decode_vp9.c`, `src/decode_av1.c`, `src/decode_h264.c` —
+  per-codec block walkers
+- `src/frame_io.c` — frame allocation, return to kernel
+
+## License
+
+BSD-2-Clause (matches daedalus-fourier sibling).
+
+## Phase 8.3 starting point
+
+A standalone program that:
+1. Opens a .ivf or .mp4
+2. Pulls codec packets via dlopen'd avformat
+3. Calls dlopen'd avcodec to parse (without decoding)
+4. Walks the block-level metadata
+5. Validates output structure
+
+No kernel involvement yet — just confirm the parse path works.