Docs: fix stale directory structure in planning.md

Add missing modules (config, discovery, reconciler, ingest) and update
node description from "later" to reflect its current done state.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

planning.md

@@ -15,14 +15,18 @@ video-setup/
   src/
     modules/
       common/        - shared definitions (error types, base types)
+      config/        - INI file loader with schema-driven defaults, typed getters
       media_ctrl/    - Linux Media Controller API (topology, pad formats, links)
       v4l2_ctrl/     - V4L2 camera controls (enumerate, get, set)
       serial/        - little-endian binary serialization primitives
       transport/     - framed TCP stream, single-write send
+      discovery/     - UDP multicast announcements, peer table, found/lost callbacks
       protocol/      - typed write_*/read_* message functions
       test_image/    - test pattern generator (colour bars, ramp, grid; YUV420/BGRA)
       xorg/          - GLFW+OpenGL viewer sink; stub for headless builds
-    node/            - video node entry point and top-level integration (later)
+      reconciler/    - generic wanted/current state machine reconciler
+      ingest/        - V4L2 capture loop, MMAP buffers, on_frame callback
+    node/            - video node binary (source + display sink roles)
   include/           - public headers
   dev/
     cli/             - exploratory CLI drivers, one per module