Add wiki/ folder with functional description + draw.io diagrams

Moves documentation into the code repo so code, docs, and diagrams
version-lock and review together. Previous location was
pumpingStation.wiki.git; that will shrink to a pointer.

Contents:
- wiki/README.md — doc index
- wiki/functional-description.md — operator-facing reference derived
  from src/specificClass.js: basin model, net-flow selection,
  level-based control zones, safety interlocks, registration topology
- wiki/diagrams/ — editable draw.io sources paired with SVG exports
  (basin-model, control-zones, safety-rules) + README with the
  open/edit/export/commit workflow

The .drawio files are rough starters; iterate in draw.io and re-export.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

wiki/README.md

@@ -0,0 +1,15 @@
+# pumpingStation — Documentation
+
+All docs and diagrams for this node live in this folder so they version-lock with the code they describe.
+
+## Pages
+
+- **[Functional Description](functional-description.md)** — operator-facing reference derived from `src/specificClass.js`: basin model, net-flow selection, level-based control zones, safety interlocks, registration topology.
+
+## Diagrams
+
+Editable draw.io sources live in [`diagrams/`](diagrams/). See [`diagrams/README.md`](diagrams/README.md) for the editing workflow — open `.drawio` files in [draw.io](https://app.diagrams.net/), export to `.drawio.svg`, commit both.
+
+## Part of
+
+This node is a git submodule of [EVOLV](https://gitea.wbd-rd.nl/RnD/EVOLV). The EVOLV superproject has its own [`wiki/`](https://gitea.wbd-rd.nl/RnD/EVOLV/src/branch/main/wiki) with platform-level docs (architecture, concepts, shared manuals).