docs: Folder & File Layout section + flag vgc.{js,html} naming drift

Entry/HTML files should be valveGroupControl.{js,html} to match the folder
name. Rename when the file is next touched. Full rule:
.claude/rules/node-architecture.md in the EVOLV superproject.

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

CLAUDE.md

@@ -21,3 +21,28 @@ Key points for this node:
 - Stack same-level siblings vertically.
 - Parent/children sit on adjacent lanes (children one lane left, parent one lane right).
 - Wrap in a Node-RED group box coloured `#50a8d9` (Unit).
+
+## Folder & File Layout
+
+Every per-node file MUST use the folder name (`valveGroupControl`) **exactly**, case-sensitive. Full rule: [`.claude/rules/node-architecture.md`](https://gitea.wbd-rd.nl/RnD/EVOLV/src/branch/development/.claude/rules/node-architecture.md) in the EVOLV superproject.
+
+| Path | Required name |
+|---|---|
+| Entry file | `valveGroupControl.js` |
+| Editor HTML | `valveGroupControl.html` |
+| Node adapter | `src/nodeClass.js` |
+| Domain logic | `src/specificClass.js` |
+| Editor JS modules | `src/editor/*.js` (extract when inline editor JS exceeds ~50 lines) |
+| Tests | `test/{basic,integration,edge}/*.test.js` |
+| Example flows | `examples/*.flow.json` |
+
+> ⚠️ **Legacy naming drift in this repo** — to be renamed when the file is next touched:
+>
+> | Path | Currently | Should be |
+> |---|---|---|
+> | Entry file | `vgc.js` | `valveGroupControl.js` |
+> | Editor HTML | `vgc.html` | `valveGroupControl.html` |
+>
+> Renames require updating: the file itself, `package.json#node-red.nodes`, any `require()` / `import` paths, and superproject submodule references in one commit.
+
+When adding new files, read the rule above first to avoid drift.