feat(protocol): carry complete encoded media frames

frames/datagram-v2.md

@@ -0,0 +1,31 @@
+# VerseVDI complete media datagram v2
+
+Datagram v2 carries one complete encoded video or audio unit under one sequence.
+It is negotiated explicitly as `datagram-v2`; v1 bytes are never reinterpreted.
+The gateway relays encoded bytes without codec processing or provider exposure.
+
+All multi-byte integers are unsigned big-endian. The fixed header is 23 bytes:
+
+| Offset | Size | Field | Rule |
+|---:|---:|---|---|
+| 0 | 2 | magic | ASCII `VD` (`0x56 0x44`) |
+| 2 | 1 | version | `2` only |
+| 3 | 1 | channel | `media.video.v1` (10) or `media.audio.v1` (11) |
+| 4 | 1 | flags | zero; unknown bits reject |
+| 5 | 4 | sequence | session-local wrapping complete-unit sequence |
+| 9 | 8 | timestamp_ms | sender timestamp, bounded by transport skew policy |
+| 17 | 2 | fragment_index | zero-based |
+| 19 | 2 | fragment_count | 1 through 891; index less than count |
+| 21 | 2 | payload_length | exact payload byte count, at most 1,177 |
+
+Each QUIC datagram is at most 1,200 bytes. One complete unit is at most
+1,048,576 encoded bytes and 891 fragments. A sender rejects a larger unit
+before fragmentation.
+
+A receiver retains at most four incomplete media units and only received
+fragment bytes. Fragments for one unit must agree on channel, sequence,
+timestamp, flags, and count. Exact duplicates are ignored; conflicting
+duplicates reject that unit. Bounded reorder is accepted. An incomplete unit
+expires after 250 milliseconds, and accepting a fifth incomplete unit evicts
+the oldest. Reassembly checks the 1,048,576-byte ceiling before appending and
+emits only after every fragment is present.

frames/registry.json

@@ -1,6 +1,7 @@
 {
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "version": "1",
+  "framing_profiles": ["datagram-v1", "datagram-v2"],
   "header_bytes": 21,
   "maximum_frame_bytes": 65536,
   "channels": [