feat(video+desktop): camera capture, video UI, E2E AEAD wiring, test fixes

Blockers 4 & 5: browser getUserMedia → JPEG IPC → Rust I420 pipeline;
remote video strip renders decoded frames via canvas; EncryptingTransport
wraps QuinnTransport so WZP AEAD is applied to all media (C2 fix).

Test fixes: HandshakeResult.session destructuring across relay/client/crypto
integration tests; video_codecs field added to all CallOffer/CallAnswer
structs; wzp-video pipeline_roundtrip integration tests added.

PRD docs: five Kimi-ready specs for E2E encryption, Android NDK 0.9 migration,
quality upgrade flow, wire-format hardening, and clippy debt.

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

crates/wzp-client/src/call.rs

@@ -565,7 +565,7 @@ impl CallDecoder {
         // ignored — a graceful mixed-version degradation).
         if !packet.header.codec_id.is_opus() {
             let _ = self.fec_dec.add_symbol(
-                (packet.header.fec_block & 0xFF) as u8,
+                packet.header.fec_block,
                 packet.header.fec_block >> 8,
                 packet.header.is_repair(),
                 &packet.payload,