Fold typed-message and UI-managed-secrets decisions into the roadmap

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012be4pBsRZ1EQX8RNv8zrDX

ROADMAP.md

@@ -1,11 +1,11 @@
 # Roadmap
 
 Component-level breakdown. The milestone-level master (M1–M5, with the vision
-decisions behind it) is `docs-private/roadmap.md` in the workspace root repo.
+decisions behind it) is `docs/private/roadmap.md` in the docs submodule.
 
 Implementation strategy and record of existing/planned features. Completed items are
-terse checklists — the requirement detail lives in `docs/architecture/overview.md` (software requirements,
-evaluated tooling, hardware) and `docs/architecture/structure.canvas` (the four-way component split).
+terse checklists — the requirement detail lives in `docs/private/vision.md` (goals,
+requirements, decisions) and `docs/architecture/structure.canvas` (the four-way component split).
 Remaining tasks keep enough scope to be actionable.
 
 Legend: `[x]` done · `[ ]` planned · sub-lists split done vs. remaining for partial items.
@@ -35,6 +35,11 @@ external interfaces. See `docs/architecture/structure.canvas` → *Backend – M
 - [x] Node types: HTTP, MQTT, InfluxDB, Delay, MLP
 - [ ] Make `app/flow` an importable package (`__init__.py`, absolute `app.flow.*` imports)
       — nothing can consume it until this lands
+- [ ] Typed, serializable node I/O: declared input/output schemas (Pydantic),
+      JSON-serializable messages with explicit binary codecs, no pickle in the
+      state backends
+- [ ] Secrets/credentials store for node integrations managed via the API/UI;
+      `.env` bootstrap-only
 - [ ] Persistence models for flows, nodes, edges and node source, replacing the
       filesystem-and-hot-reload prototype
 - [ ] REST + WebSocket API over the engine: create/read/update flows, run, stream results