docs(logic): document panel-logic array locals

Document array-valued local variables (statevar type=array with
elem/sizing/capacity), the value-polymorphic expression engine and array
functions, the array.* mutation nodes, accumulate/export unification, and
index-aligned CSV export in TECHNICAL_SPEC §3.8. Note in TODO that panel-logic
(Phase 1) array support is complete while the server-side control-logic port
(Phase 2) remains pending.

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

TODO.md

@@ -98,6 +98,7 @@
     - [x] Implement live / debug mode where value are evaluated online and visualized at human speed (e.g. 0.5s) — editor spins up a second client-side `LogicEngine` in new `dryRun` mode (real writes/config/dialogs suppressed) loaded with the edited graph; per-node values polled into the shared badges; the view-mode singleton is untouched
     - add full suppor to local array values: dynamic, dynamic but capped max, fixed size etc:
       - array functions should work with new local array
+      - NOTE: **Phase 1 (panel logic, client-side TS) is DONE** — array statevars (dynamic/capped/fixed), value-polymorphic expression engine with indexing + array functions, `action.array.*` mutation nodes (legacy accumulate/export/clear unified + auto-migrated), panel-XML round-trip, editor declaration form, and widget array modes (plot/table/multi-LED). Box stays unchecked until **Phase 2** (server-side `internal/controllogic` Go port, see below) lands.
   - [ ] Control loop:
     - [x] Implement live / debug mode where value are evaluated online and visualized at human speed (e.g. 0.5s) — server pushes per-node events over the WS (`debugSubscribe`/`debugNode`) via a new `DebugObserver` on the engine (lock-free `atomic.Value`, gated by a per-graph watch set) + `internal/server/debughub.go` (drop-on-full fan-out). Two modes share one message shape: **Live** observes the running enabled graph; **Simulate** dry-runs the unsaved edits in a throwaway sandbox (`StartSimulate`, side effects suppressed). Live/Sim sub-toggle in the editor
     - add full support to server side array values