build: speed up rust image builds and validate env

TASKS.md

@@ -2,19 +2,21 @@
 
 ## Current
 
-### `feat/websocket-test-run-polish`
+### `feat/rust-docker-build-cache`
 
-Status: pending
+Status: in_progress
 
 DoD:
-- WebSocket wizard test-run shows reconnect / bounded-result semantics clearly
-- WebSocket test-run flow is covered by local fixtures and Playwright
-- `TASKS.md` stays aligned with the actual streaming branch state
+- Rust Docker builds use a cache-friendly multi-stage layout
+- `admin-api` and `mcp-server` reuse dependency layers across rebuilds
+- noisy local artifacts are excluded from Docker build context
+- deployment fails early when required secret-store env is missing
 
 ## Next
 
-- `feat/live-authenticated-staging-entry`
+- `feat/websocket-test-run-polish`
 
 ## Backlog
 
+- `feat/websocket-test-run-polish`
 - `feat/live-authenticated-staging-entry`