wshub: fix CalConfig.Normalise parity gaps vs C++ twin and JS client

Finding 1: strip trailing [digits] array-element suffix from Signal so one
calibration entry covers an entire array signal, matching the C++ strchr
truncation and the JS equivalent.

Finding 2: after the 16-byte Unit truncation, drop any trailing partial UTF-8
rune so json.Marshal never emits replacement characters; keeps byte limit in
sync with C++ strncpy(u, unit, kMaxUnitLen).

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

Common/Client/go/wshub/calibration.go

@@ -4,11 +4,18 @@ import (
 	"encoding/json"
 	"log"
 	"math"
+	"regexp"
 	"sort"
 	"strings"
 	"sync"
+	"unicode/utf8"
 )
 
+// arrayIndexSuffix matches a trailing "[digits]" at the very end of a signal
+// name, used to strip array-element suffixes so one entry covers the whole
+// array.  Mirrors the C++ `strchr(signal,'[')` truncation and the JS equivalent.
+var arrayIndexSuffix = regexp.MustCompile(`\[\d+\]$`)
+
 // maxUnitLen bounds the calibration unit override.  Mirrored by kMaxUnitLen in
 // the C++ StreamHub and MAX_UNIT_LEN in the SPA's calibration.js.
 const maxUnitLen = 16
@@ -37,6 +44,10 @@ func calKey(source, signal string) string { return source + "\x00" + signal }
 func (c *CalConfig) Normalise() bool {
 	c.Source = strings.TrimSpace(c.Source)
 	c.Signal = strings.TrimSpace(c.Signal)
+	// Strip a trailing "[digits]" suffix so one entry covers an entire array
+	// signal.  "Adc[3]" → "Adc".  Must run before the empty check below so
+	// that "[0]" → "" → rejected, matching C++ and JS behaviour.
+	c.Signal = arrayIndexSuffix.ReplaceAllString(c.Signal, "")
 	if c.Source == "" || c.Signal == "" {
 		return false
 	}
@@ -49,6 +60,16 @@ func (c *CalConfig) Normalise() bool {
 	c.Unit = strings.TrimSpace(c.Unit)
 	if len(c.Unit) > maxUnitLen {
 		c.Unit = c.Unit[:maxUnitLen]
+		// The byte cut may land mid-rune.  Drop any trailing partial rune so
+		// the result is always valid UTF-8; json.Marshal would otherwise emit
+		// replacement characters and break the save→load round-trip.
+		for {
+			r, size := utf8.DecodeLastRuneInString(c.Unit)
+			if r != utf8.RuneError || size != 1 {
+				break
+			}
+			c.Unit = c.Unit[:len(c.Unit)-1]
+		}
 	}
 	return true
 }