svc-vision: camera live view, moved from app-flutter's test tool

Camera-agnostic (--camera auto finds any V4L2 capture device and finds it
again after a replug; non-MJPEG cameras are encoded), says when the camera
is unavailable, paced per decision 28. Python, standard library only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

docs/impl/plans/INITIAL.md

@@ -0,0 +1,31 @@
+---
+type: plan
+status: active
+updated: 2026-10-12
+---
+# Initial plan
+
+## Scope
+
+The camera end to end on the Orin: capture, the live view, recording, and later
+inference. Hardware facts for the current camera are in orin-nano-env-setup
+`docs/impl/reports/USB-CAMERA.md`; tablet link limits in app-flutter
+`docs/impl/reports/LINK-TEST-2026-10-11.md`.
+
+## Order
+
+0. **Live view** — in place: `src/liveview.py` as `yukart-vision.service` on
+   `:7710`. Started as a test tool in app-flutter and moved here once the live
+   view became a product feature (decision 27). Protocol in the module docstring.
+1. **Capture fan-out.** One capture process, frames to several consumers (live
+   view, recorder, inference). Needed before a second consumer exists.
+2. **Recording.** H.264 in software (`x264enc`, ~1.3–2 cores at 1080p) in
+   segments on the recorder's sessions, under the recordings bound.
+3. **Exposure for sign reading.** Manual exposure with own metering to hold the
+   frame rate; LED signs flicker under short exposures.
+4. **Inference** — deferred (decision 7): road signs, speed limits first.
+
+## Open
+
+- The protocol lives in the docstring. It moves to contracts when a second
+  client exists or it changes shape.