feat(transport-ws,transport-contract): multiplex chat ops onto the surface WS

Add chat WS ops (chat.send / chat.delta / chat.error) + unified
WsClientMessage/WsServerMessage unions to @dispatch/transport-contract
(imports ui-contract; surface protocol unchanged — additive non-colliding
type variants, no channel wrapper). transport-ws drives
sessionOrchestrator.handleMessage, streaming each AgentEvent as chat.delta
over the same connection that carries surface ops; per-connection
AbortController cancels in-flight turns on socket close; error-isolated.

Verified live: one WS connection delivered the surface catalog AND a real
flash chat turn (chat.delta stream, reply 'Hello my friend').

Completes the FE Slice 2 backend prereqs. typecheck clean, 485 vitest + 80 bun,
biome clean.

Discovered (separate, pre-existing): runtime does not emit
turn-start/done/turn-sealed on either transport — needed for FE cache-commit;
tracked in tasks.md.

1 files changed, 3 insertions, 0 deletions

diff --git a/bun.lock b/bun.lock
index b8f9bde..dd7c6ff 100644
--- a/bun.lock
+++ b/bun.lock
@@ -143,6 +143,7 @@
       "name": "@dispatch/transport-contract",
       "version": "0.0.0",
       "dependencies": {
+        "@dispatch/ui-contract": "workspace:*",
         "@dispatch/wire": "workspace:*",
       },
     },
@@ -163,7 +164,9 @@
       "version": "0.0.0",
       "dependencies": {
         "@dispatch/kernel": "workspace:*",
+        "@dispatch/session-orchestrator": "workspace:*",
         "@dispatch/surface-registry": "workspace:*",
+        "@dispatch/transport-contract": "workspace:*",
         "@dispatch/ui-contract": "workspace:*",
       },
     },