Draft Milestone 4 scope and mark progress in docs

docs/PROGRESS.md

@@ -60,3 +60,18 @@ Delivered:
 
 Git:
 - Tag: `v0-m3-done`
+
+## Milestone 4 - Interactive SSH Session UX
+
+Status: In Progress
+
+Started:
+- Milestone 4 draft added to spec
+- Interactive SSH terminal panel wiring started (backend output stream + input send path)
+- Host-key confirmation request/response signal flow added (`Ask` policy path)
+- `known_hosts_policy` defaults and profile dialog options updated to include `Ask`
+
+Pending:
+- End-to-end interactive behavior hardening across Linux/macOS/Windows
+- Terminal UX polish (control keys, resize behavior, output formatting)
+- Additional diagnostics and integration test coverage for reconnect/auth/host-key scenarios