Phase 8.7: media controller + multi-frame streaming verification

Two pieces — both shipped:

1. Media controller binding closes the last v4l2-compliance
   failure from 8.6 (DECODER_CMD, which requires has_media on
   stateless decoders) and unlocks the V4L2 request API for
   libva-v4l2-request.

2. Multi-frame streaming test exercises the daemon's
   AVCodecContext state preservation across many REQ_DECODE
   calls — Phase 8.6's tests pushed exactly one keyframe per
   invocation; real content has P-frame references.

Compliance now reaches **49/49 passing.**

Kernel (kernel/daedalus_v4l2_main.{c,h}):
- Added `struct media_device mdev` to daedalus_dev.
- media_device_init(&mdev) BEFORE v4l2_device_register so
  v4l2-core sees v4l2_dev.mdev = &mdev and binds the m2m
  entities into the graph during register.
- After video_register_device:
  v4l2_m2m_register_media_controller(..., MEDIA_ENT_F_PROC_VIDEO_DECODER)
  then media_device_register so userspace sees the complete
  graph in /dev/mediaN with the decoder entity tagged.
- daedalus_remove unwinds in reverse: unregister media,
  unregister mc, unregister video, release m2m, unregister
  v4l2, cleanup mdev.
- Error paths added for both new failure points.

Test harness (tools/test_m2m_stream.c, new):
- Multi-frame V4L2 m2m client: parses IVF → 4-deep buffer
  rings on both queues → per-frame QBUF/DQBUF loop →
  concatenates decoded NV12 to output file. Returns 0 only
  if every input frame decoded without error.
- Same codec vocabulary as test_m2m_decode (vp9 | av1 |
  h264 via 5th arg).

Verification on hertz (Pi 5, 6.12.75+rpt-rpi-2712):

v4l2-compliance: 49 tests, 49 passed, 0 failed, 0 warnings.

  $ v4l2-ctl --list-devices
  daedalus-fourier V3D7+NEON (platform:daedalus_v4l2):
        /dev/video0
        /dev/media3

VP9 320×240 30 frames (1 keyframe + 29 P-frames, 3.46 MB
NV12): byte-for-byte match vs `ffmpeg -i in.ivf -pix_fmt
nv12 -f rawvideo`.

VP9 1920×1080 10 frames (31 MB NV12 through the dmabuf
path): byte-for-byte match vs same reference command.

Daemon log shows cookies 1..30 all completing cleanly in
order; lazily-opened AVCodecContext maintains reference
frames across the chardev round-trips.

Clean SIGTERM + rmmod, no oops/WARN.

Roadmap update (docs/roadmap.md):
- 8.7 marked closed with closure-doc reference.
- 8.8 reshaped: perf profiling, QPU dispatch substitution
  via daedalus-fourier, multi-frame AV1/H.264, HDR (P010M).

Per correctness-before-speed:
- Order-correct media controller lifecycle (init → bind
  v4l2_dev → register video → register mc → register
  media; reverse for teardown).
- 4-deep buffer rings on both queues — the scheduler
  actually pipelines multiple in-flight cookies through
  the chardev (not just one-at-a-time as in 8.5/8.6 tests).
- Bit-exact comparison against ffmpeg, not "looks right."
- All resource paths cleaned on every error branch.

Phase 8.8 next: profile daemon hot loops, dlopen
daedalus-fourier from the daemon, swap FFmpeg per-block
calls for daedalus_dispatch_* where the kernel matches,
target 30fps@1080p from 30fps-floor-is-fine memory.

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

docs/roadmap.md

@@ -77,24 +77,41 @@ See `docs/phase_8_5_closure.md`.
 
 See `docs/phase_8_6_closure.md`.
 
-### Phase 8.7 — media controller, perf, HDR, long-form streams
+### Phase 8.7 — media controller + multi-frame streaming (closed 2026-05-18)
 
-1. Media controller binding via
-   `v4l2_m2m_register_media_controller` (closes the last
-   v4l2-compliance fail and unlocks the request API).
-2. Profile the daemon's per-frame cost on hertz; substitute
-   `daedalus_dispatch_*` for FFmpeg's per-block paths where
-   the kernel implementation matches.  Target the
-   `30fps-floor-is-fine` memory's daily-YouTube criterion:
-   30fps@1080p with CPU left over for vscode.
-3. HDR / 10-bit support — P010M CAPTURE, depth-aware
-   `pack_nv12_to_planes`.
-4. Long-form multi-frame streaming tests (B-frame refs,
-   GOP boundaries) — current test client is one keyframe
-   per run.
+- Media controller bound via
+  `v4l2_m2m_register_media_controller` +
+  `media_device_register`; `/dev/mediaN` published.
+- `tools/test_m2m_stream` parses IVF and pushes frames
+  sequentially through a 4-deep buffer ring; daemon
+  AVCodecContext preserves reference frames across calls.
+- 30-frame VP9 320×240 stream byte-exact (3.46 MB across
+  1 keyframe + 29 P-frames).
+- 10-frame VP9 1080p stream byte-exact (31 MB across
+  10 frames at full HD).
+- v4l2-compliance: **49/49 passing** (was 47/48 in 8.6;
+  media controller added a 49th test and closed DECODER_CMD).
 
-Deliverable: 30fps stable on real content + full
-compliance pass.
+See `docs/phase_8_7_closure.md`.
+
+### Phase 8.8 — perf, QPU dispatch, AV1/H.264 streams, HDR
+
+1. Profile daemon end-to-end on hertz; identify FFmpeg hot
+   functions per codec.
+2. dlopen daedalus-fourier's per-kernel entry points from
+   the daemon; substitute `daedalus_dispatch_*` for FFmpeg's
+   matching per-block calls (IDCT 4×4 / 8×8, MC, deblock,
+   qpel — from cycles 1, 2, 4, 9).
+3. Validate bit-exactness after each substitution.
+4. Hit 30fps@1080p stable on VP9 — the
+   `30fps-floor-is-fine` memory's user-facing criterion.
+5. Multi-frame AV1 + H.264 round-trips (extend stream
+   tests).
+6. HDR / 10-bit (P010M CAPTURE, depth-aware
+   `pack_nv12_to_planes`).
+
+Deliverable: 30fps stable on real content across all
+three codecs.
 
 ## Effort estimate