docs: fix three review findings in calibration documentation

- Finding 1 (Critical): replace "16 chars" with "16 UTF-8 bytes" in the
  setCalibration unit field description (StreamHub-API.md) and the Cal·Unit
  toolbar row (WebUI.md); note that multi-byte characters consume more than
  one byte and that truncation never splits a character.

- Finding 2 (Important): correct the claim that a sources broadcast after
  reloadConfig is conditional on new sources being added — that is true only
  of the Go hub. The C++ hub calls BroadcastSources() unconditionally on
  success. Both the reloadConfig command description and the configReloaded
  event description in StreamHub-API.md are updated; the Reload bullet in
  WebUI.md is updated with a brief note. Clients must tolerate an unsolicited
  sources frame after any reload.

- Finding 3 (Minor): the configSaved failure example used "no SourcesFile
  configured", which matches neither hub. Corrected to the C++ form
  "no sources file configured" and added a note that the exact error text
  is not part of the protocol contract (Go uses "no sources-file configured").

Source evidence: calibration.go (maxUnitLen, len(), rune-repair loop),
StreamHub.cpp (kMaxUnitLen, byte strncpy, HandleReloadConfig unconditional
BroadcastSources, HandleSaveSources error string).

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

Docs/StreamHub-API.md

@@ -66,7 +66,7 @@ name — one entry covers every element of an array signal.
 | `signal` | string | — | non-empty after trimming; any trailing `[i]` is stripped |
 | `scale` | number | `1` | finite and non-zero |
 | `offset` | number | `0` | finite |
-| `unit` | string | `""` | trimmed, truncated to 16 chars; empty = use the streamer's own unit |
+| `unit` | string | `""` | trimmed, truncated to 16 UTF-8 bytes (a multi-byte character such as `°C` consumes more than one byte; truncation never splits a character); empty = use the streamer's own unit |
 
 Calibration is **metadata only**: the hub stores and redistributes it but never
 applies it. Ring buffers, recorded history, the `zoom` reply, both binary frames
@@ -96,7 +96,11 @@ a live UDP session that must not be interrupted. An unsaved source the user adde
 keeps streaming.
 
 The hub replies with [`configReloaded`](#configreloaded), followed on success by a
-`calibration` broadcast and a `sources` broadcast.
+`calibration` broadcast. Whether a `sources` broadcast follows depends on the
+hub implementation: the Go hub emits `sources` only when the file adds at least
+one new source (each `sm.Add()` call triggers it individually), while the C++
+hub always emits `sources` unconditionally after a successful reload. Clients
+must therefore tolerate an unsolicited `sources` frame after any reload.
 
 ### `getSources` / `getConfig` / `getStats`
 
@@ -284,10 +288,12 @@ after a successful `reloadConfig`. It is a separate frame rather than a field on
 
 ```json
 {"type":"configSaved","ok":true,"path":"/etc/streamhub/sources.json"}
-{"type":"configSaved","ok":false,"path":"","error":"no SourcesFile configured"}
+{"type":"configSaved","ok":false,"path":"","error":"no sources file configured"}
 ```
 Broadcast in reply to `saveSources`. `path` is always present (empty when the hub
-has no config file configured); `error` only when `ok` is false.
+has no config file configured); `error` only when `ok` is false. The exact error
+text is not part of the protocol contract and differs between hubs (the Go hub
+uses `"no sources-file configured"`, the C++ hub `"no sources file configured"`).
 
 ### `configReloaded`
 
@@ -295,9 +301,11 @@ has no config file configured); `error` only when `ok` is false.
 {"type":"configReloaded","ok":true,"path":"/etc/streamhub/sources.json"}
 {"type":"configReloaded","ok":false,"path":"/etc/streamhub/sources.json","error":"cannot read sources file"}
 ```
-Broadcast in reply to `reloadConfig`; same shape as `configSaved`. On success it
-is followed by a `calibration` broadcast and, if the file added any source, a
-`sources` broadcast.
+Broadcast in reply to `reloadConfig`; same shape as `configSaved`. On success
+it is followed by a `calibration` broadcast. Whether a `sources` broadcast also
+follows is hub-specific: the Go hub sends it only if the reload added at least
+one new source; the C++ hub sends it unconditionally. Clients must tolerate an
+unsolicited `sources` frame after any reload.
 
 ---
 

Docs/WebUI.md

@@ -91,7 +91,9 @@ At the bottom of the sidebar, the collapsible **Sources & Config** section holds
   config file;
 - **Reload** — re-reads that file. Calibration is replaced wholesale (so unsaved
   edits are discarded), sources present in the file but not running are added,
-  and no running source is stopped or reconnected;
+  and no running source is stopped or reconnected. The hub may send an updated
+  `sources` list even when nothing changed (see the API doc for the per-hub
+  difference);
 - a status line showing the written path on success or the hub's error text on
   failure.
 
@@ -160,7 +162,7 @@ plot header showing per-signal vertical scale controls:
 | **Type** (Mixed mode only) | Toggle between **Analog** and **Digital** for this signal |
 | **Cal · Scale** | Data calibration gain. `value = raw × Scale + Offset` |
 | **Cal · Offset** | Data calibration bias, in calibrated units |
-| **Cal · Unit** | Overrides the unit reported by the streamer (max 16 chars) |
+| **Cal · Unit** | Overrides the unit reported by the streamer (max 16 UTF-8 bytes; a multi-byte character such as `°C` counts as more than one byte) |
 | **Reset** | Clears this signal's calibration (`Scale = 1`, `Offset = 0`, no unit override) |
 | **✕** | Close the toolbar and deselect the signal |