Update future-plans: dual event bus, UI sub-project boundary, fix duplicate

- Replace simple SSE note with full dual-bus architecture:
  server EventEmitter + client pub/sub, SSE as bridge, effects/ pattern,
  mutation wrapper to avoid wildcard, collection-level event granularity
- Add 'UI as self-contained sub-project' section: composition root pattern,
  main.mjs vs mock-main.mjs entry points, mock-api contract, views-never-
  call-each-other discipline
- Expand app.mjs monolith note to mention mount() export pattern
- Remove duplicate CodeMirror paragraph (copy-paste artifact)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

future-plans.md

@@ -23,20 +23,52 @@ undo, audit trails, and debugging data corruption.
 
 ## Real-time / live updates
 
-### Server-sent events for data changes
-When data changes on the server (upload, edit, delete — from any client), connected
-browsers should receive a notification and update the affected view automatically.
-Use case: uploading photos from a phone while the desktop browser has the Images or
-Bins section open.
+### Dual event bus architecture
 
-Server-sent events (SSE) are the natural fit — lightweight, one-directional, no
-library needed. The server emits a change event with a `type` (e.g. `source_images`,
-`bins`) and the client re-fetches and re-renders only the affected collection.
-Views that aren't currently visible don't need to do anything — they'll reload on
-next navigation.
+Two independent buses, bridged by SSE:
 
-Ties directly into the delta tracking plan: the same write path that appends to the
-delta log can also fan out to connected SSE clients.
+**Server bus** (`lib/bus.mjs`, Node `EventEmitter`):
+- Route handlers emit a specific event after each mutation (`field:deleted`,
+  `bin:changed`, etc.) and nothing else — side effects are not inline
+- Effect modules in `server/effects/` subscribe and handle cascading work:
+  - `field-effects.mjs` — strips deleted field from all components/bins/bin types
+  - `sse-effects.mjs` — broadcasts mutations to connected SSE clients
+  - `audit-effects.mjs` — writes delta log (future)
+  - `bin-effects.mjs` — e.g. propagates type dimension changes to bins
+- New cross-cutting concerns (audit, cache invalidation, notifications) are
+  additional listeners — route handlers never grow
+
+**Client bus** (`lib/bus.mjs`, lightweight pub/sub or `EventTarget`):
+- `api.mjs` emits on the bus after every successful mutation
+- `sse.mjs` (SSE connection client) translates incoming server events to bus emits
+- View modules subscribe to relevant events and re-render; they never call each other
+- `mock-api.mjs` also emits on the same bus after in-memory mutations, so views
+  react correctly in mock mode without any SSE
+
+**SSE bridge**: `sse-effects.mjs` on the server broadcasts to connected clients;
+`sse.mjs` on the client receives and re-emits on the client bus. Views are unaware
+of whether a change was local or remote.
+
+**Avoiding wildcard listeners**: instead of a wildcard `*` listener (not natively
+supported by `EventEmitter`), emit a generic `mutation` event alongside every
+specific event. The SSE broadcaster listens to `mutation`; everything else listens
+to specific events. New event types are automatically forwarded without touching
+the broadcaster.
+
+```js
+function emit(event, data) {
+    bus.emit(event, data);
+    bus.emit('mutation', { event, data });
+}
+```
+
+**Event granularity**: collection-level events are sufficient (`bins:changed`,
+`components:changed`). Passing the affected id or record is optional — views can
+use it to do a targeted update or ignore it and re-fetch the collection. Fine-grained
+events are an optimisation to add later if full-collection re-fetches become slow.
+
+Ties into the delta tracking plan: `audit-effects.mjs` is another bus listener —
+the same mutation path that drives SSE also drives the delta log.
 
 ## App architecture
 
@@ -69,10 +101,39 @@ const SECTION_RENDERERS = {
 function render() { sync_nav(); SECTION_RENDERERS[section]?.(); }
 ```
 
+### UI as a self-contained sub-project
+
+The UI boundary is `api.mjs` — every piece of data the UI touches goes through
+named exports in that file. This seam should be made explicit so the UI can be
+developed and tested against a mock without a running server.
+
+**Composition root / dependency injection**: `app.mjs` should not import `api.mjs`
+directly. Instead it receives the api implementation as a parameter. Two thin entry
+files wire it up:
+
+```
+main.mjs       — imports real api.mjs, passes to app.start()
+mock-main.mjs  — imports mock-api.mjs, passes to app.start()
+```
+
+`mock-main.mjs` is a separate deployable (e.g. served at `/mock` or on a dev port),
+not a URL flag. The app has no runtime knowledge of which implementation it received.
+
+**mock-api.mjs**: same exports as `api.mjs`, backed by in-memory arrays seeded with
+realistic fixture data. Mutations update the in-memory state so the UI behaves
+realistically (add/delete/edit all persist within the session). Also emits on the
+client bus so cross-view reactivity works identically to the real app. No SSE
+connection needed in mock mode — the bus events come from the mock mutations.
+
+**Views never call each other**: once split into modules, `views/bins.mjs` must
+not import `views/inventory.mjs`. Cross-section reactions happen exclusively through
+the client bus. This is the main structural discipline that makes the split work.
+
 ### app.mjs monolith
-`app.mjs` is large. Consider splitting into per-section modules
-(`views/components.mjs`, `views/grids.mjs`, etc.) that each export their render
-function and own their local state.
+`app.mjs` is large. Split into per-section view modules (`views/components.mjs`,
+`views/grids.mjs`, `views/bins.mjs`, etc.) each owning its local state, subscribing
+to bus events at init, and exporting a single `mount(container)` function. The
+composition root (`main.mjs`) imports all view modules and registers them.
 
 ### Split CSS into per-section files
 `style.css` is a single large file and getting hard to navigate. Split into
@@ -328,10 +389,6 @@ slot targets) in addition to custom formatters.
 This revision also applies to field parsers and search view expressions once those
 exist — they all follow the same pattern of JS function → structured output →
 context-specific renderer.
-Any field that accepts JavaScript (name formatter templates, future custom search
-views, field parsers, etc.) should use a CodeMirror 6 editor instead of a plain
-`<textarea>`. Gives syntax highlighting, bracket matching, and a proper editing
-experience for JS snippets.
 
 ## Search & views