Inline /rate and /pitch controls handled by the wrapper; docs

docs/TTS-DESIGN.md

@@ -371,6 +371,26 @@ Other NetTTS features and their relevance:
   our prefix runs the engines with builtin Wine libraries.
 - Win32 GUI and preset sliders: Veskslop provides the UI.
 
+### Inline rate/pitch controls (engine-side)
+
+The wrapper consumes NetTTS-style, line-leading controls, so Veskslop and the WebUI do
+not need to parse or implement them:
+
+    /rate 150 Attention all personnel.      # 150% rate, then the line
+    /pitch 90 Attention all personnel.      # 90% pitch
+    /rate 120 /pitch 110 Inbound tram.      # both, in any order
+
+- `N` is a percent (100 = normal, clamped to 0-200); values `<= 2.0` are multipliers
+  (`/rate 1.5` = 150%).
+- They override `VESKSLOP_TTS_SPEED` / `VESKSLOP_TTS_PITCH` for that line and are not
+  spoken.
+- A line that contains only controls yields 100 ms of silence, so the daemon always
+  receives a valid WAV.
+- Rate maps through the normal speed scale; pitch percent maps to semitones
+  (`st = 12*log2(N/100)`) and then through the per-voice natural pitch.
+- Verified on the dev host: `/rate 50` doubles the line duration; `/pitch 150` raises
+  the median F0 from 122 Hz to 177 Hz.
+
 ### Transport and latency
 
 - Installation is one command: `setup/install.sh` (system dependencies with sudo, wine