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/tests/handshake_integration.rs

@@ -91,7 +91,7 @@ async fn full_handshake_both_sides_derive_same_session() {
         wzp_relay::handshake::accept_handshake(relay_transport_clone.as_ref(), &relay_seed),
     );
 
-    let mut client_session = client_result.expect("client handshake should succeed");
+    let client_hs = client_result.expect("client handshake should succeed");
     let (mut relay_session, chosen_profile, _caller_fp, _caller_alias) =
         relay_result.expect("relay handshake should succeed");
 
@@ -122,6 +122,7 @@ async fn full_handshake_both_sides_derive_same_session() {
     let header = make_hdr(0);
     let plaintext = b"hello from client to relay";
 
+    let mut client_session = client_hs.session;
     let mut ciphertext = Vec::new();
     client_session
         .encrypt(&header, plaintext, &mut ciphertext)
@@ -180,6 +181,7 @@ async fn handshake_rejects_tampered_signature() {
             alias: None,
             protocol_version: 2,
             supported_versions: vec![2],
+            video_codecs: vec![],
         };
         client_transport_clone
             .send_signal(&offer)