feat(commands): route data.flow through the registry unit normaliser; wiki sync

- data.flow: declare unit:'m3/h' (payloadSchema any) and drop the handler's own
  convert() call — the registry now converts any number/string/{value,unit} to
  m3/h before the handler. Handler reads the normalised scalar.
- Regenerate wiki topic-contract.

data.flow integration test green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/commands/handlers.js

@@ -5,8 +5,6 @@
 // handler (the legacy nodeClass did it inline) — anything else inbound
 // is passed straight through to source.handleInput.
 
-const { convert } = require('generalFunctions');
-
 exports.cmdStart = (source, msg) => {
   source.handleInput('i_start', Boolean(msg.payload));
 };
@@ -20,17 +18,15 @@ exports.setRain = (source, msg) => {
 };
 
 exports.dataFlow = (source, msg, ctx) => {
+  // The registry has already normalised any accepted shape (number, numeric
+  // string, or { value, unit }) to a number in m3/h and tagged msg.unit.
   const log = ctx?.logger || source.logger;
-  const value = Number(msg.payload?.value);
-  const unit = msg.payload?.unit;
-  if (!Number.isFinite(value) || !unit) {
-    log?.warn?.('data.flow payload must include numeric value and unit.');
+  const value = Number(msg.payload);
+  if (!Number.isFinite(value)) {
+    log?.warn?.(`data.flow payload must be numeric, got '${JSON.stringify(msg.payload)}'.`);
     return;
   }
-  let converted = value;
-  try { converted = convert(value).from(unit).to('m3/h'); }
-  catch (err) { log?.warn?.(`data.flow unit conversion failed: ${err.message}`); return; }
-  source.handleInput('input_q', { value: converted, unit: 'm3/h' });
+  source.handleInput('input_q', { value, unit: msg.unit || 'm3/h' });
 };
 
 exports.setMode = (source, msg) => {