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-crypto/tests/featherchat_compat.rs

@@ -122,6 +122,7 @@ fn wzp_signal_serializes_into_fc_callsignal_payload() {
         alias: None,
         protocol_version: 2,
         supported_versions: vec![2],
+        video_codecs: vec![],
     };
 
     // Encode as featherChat CallSignal payload
@@ -186,6 +187,7 @@ fn wzp_answer_round_trips_through_fc_callsignal() {
         ephemeral_pub: [20u8; 32],
         signature: vec![30u8; 64],
         chosen_profile: wzp_proto::QualityProfile::DEGRADED,
+        video_codec: None,
     };
 
     let payload = wzp_client::featherchat::encode_call_payload(&answer, None, None);
@@ -309,6 +311,7 @@ fn all_signal_types_map_correctly() {
                 alias: None,
                 protocol_version: 2,
                 supported_versions: vec![2],
+                video_codecs: vec![],
             },
             "Offer",
         ),
@@ -319,6 +322,7 @@ fn all_signal_types_map_correctly() {
                 ephemeral_pub: [0; 32],
                 signature: vec![],
                 chosen_profile: wzp_proto::QualityProfile::GOOD,
+                video_codec: None,
             },
             "Answer",
         ),