fix(elevenlabs): send keyterms on the realtime STT WebSocket

[pawlowskipawel]

Problem

keyterms is accepted by elevenlabs.STT(...) but only ever sent on the batch
request. It is dropped on the realtime WebSocket path, so scribe_v2_realtime
sessions get no keyterm biasing even when the caller passes them.

ElevenLabs does support it there, as repeated keyterms query params on the connect URL:

• Realtime STT API reference lists keyterms — "List of keyterms the model is biased towards."
• Keyterm prompting guide — "also available for the realtime Speech to Text WebSocket API." Batch allows 1000 keyterms × 50 chars, realtime 50 × 20.

The docstring claims the opposite. It was accurate when written, before ElevenLabs
shipped realtime keyterms — no_verbatim, released alongside them, was wired into
_connect_ws, but keyterms was missed and the docstring never updated.

Changes

• _connect_ws appends repeated keyterms= query params, percent-encoded.
• SpeechStream.update_options accepts keyterms and triggers a reconnect, mirroring
  no_verbatim. STT.update_options forwards them to active streams.
• Docstring corrected with the real per-mode limits.
• 5 tests, following the existing enable_logging / no_verbatim patterns.

Keyterms are free-form text, unlike the other params in that URL (model ids, enums,
numbers, language codes), so they need encoding: verified against yarl.URL — the parser
aiohttp.ws_connect uses — an unescaped & splits Smith & Sons into keyterms='Smith '
plus a bogus ' Sons' param, and # truncates C# to C.
test_connect_ws_escapes_query_delimiters_in_keyterms pins this via
URL(...).query.getall("keyterms").

Verification

make check clean (ruff, mypy over 629 files). pytest tests/test_plugin_elevenlabs_stt.py — 25 passed.

Those mock the socket, so they only prove the URL is built correctly. Checked separately
against the live endpoint: one TTS-synthesized clip per term, transcribed twice over
scribe_v2_realtime — identical audio bytes in both arms, so any difference isolates
the keyterm.

term	without keyterms	with keyterms
Sonic3000	Sonic 3000	Sonic3000
GPT4o	GPT-4o	GPT4o
K2Turbo	K2 Turbo	K2Turbo
nova-3	Nova 3	nova-3
scribe-v2	Scribe V2	scribe-v2

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.