mavttsd: a pronunciation dictionary, so she says the names right (V-458)

piper reads a Russian sentence with a Russian voice, and a Latin service id
inside it comes out spelled, mangled or read as if it were a Russian word:
"Vikunja", "SearXNG", "homesrv". The lever available is the text, so the
dictionary maps a name to how it should be spelled for the voice to say it,
and mavttsd applies it at the last edge before piper — every caller's text
passes through that one point, and nothing upstream has to know how a name
sounds.

Data, not code. deploy/tts-lexicon.json ships 29 names; adding one needs a
restart of mavttsd and no rebuild of the daemon that produced the text. Off
unless -lexicon is set, like every other optional capability, and a path that
is set and unreadable stops startup — saying names wrong in silence is the
failure it exists to remove.

Two details worth keeping: the alternation is sorted longest-first, or "Home
Assistant" reads as "Хоум Assistant"; and the boundaries are written out
rather than left to \b, which is ASCII-only and never fires next to a
Cyrillic letter.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/operations.md

@@ -90,6 +90,13 @@ export LD_LIBRARY_PATH="$ROOT/deps/piper"
 
 Without `-piper` it runs as a stub.
 
+`-lexicon deploy/tts-lexicon.json` adds the pronunciation dictionary: a flat
+JSON object of name to Russian spelling, applied to the text just before piper
+reads it. It is how `Vikunja` is said as a word rather than spelled out, and how
+`SearXNG` and `homesrv` are said at all. Off unless the flag is set; a path that
+is set and unreadable stops mavttsd rather than letting it say names wrong in
+silence. Adding a name needs a restart of mavttsd and nothing else.
+
 ## mavweb — PWA voice bridge (WebSocket ↔ TCP)
 
 No CGo, no deps; builds with stock Go.