fix: lowercase bool query params on websocket connect (#712)

## Summary
  
Python's `urllib.parse.urlencode` stringifies booleans via `str()`,
producing `True`/`False`
(capitalized). The four websocket connect methods (`listen.v1`,
`listen.v2`, `speak.v1`,
`agent.v1`) all hand the encoded query dict to `urlencode`, so any
`bool` kwarg — e.g.
`diarize=True` — reaches the API as `?diarize=True` and is rejected with
HTTP 400.

The generated SDK types for these params are
`Union[Literal["true","false"], Any]` because
our AsyncAPI schemas declare them as string enums rather than `type:
boolean`. The `Any` arm
lets bools pass mypy without complaint, so the bug only surfaces on the
wire. HTTP raw
clients are unaffected because they hand params to httpx, which
lowercases bools itself.

  ## Fix
  
Add `_coerce_query_value` in `core/query_encoder.py` mapping
`True`/`False` to `"true"`/
`"false"` before `urlencode` runs. Applied at every scalar leaf site so
bools nested in
`list`/`dict` query values are also coerced. `isinstance(v, bool)` is
precise — `1`/`0` are
  not coerced (regression test confirms).

Not a breaking change: current behavior is "the call returns HTTP 400,"
so the fix can only
turn broken calls into working ones. `diarize="true"` (string) still
works identically.

`query_encoder.py` is Fern-generated; the patch is frozen under the
existing
"temporarily frozen — manual patches" pattern in `.fernignore`, with the
unfreeze condition
  documented in `AGENTS.md`.

  ## Test plan
  
  - [x] 12 new regression tests in `tests/custom/test_query_encoder.py`
  - [x] Full pytest suite: **197 passed, 4 skipped, 0 failed**
- [x] Live before/after with `diarize=True` against production —
unpatched returned HTTP
        400 (matching the reported bug); patched opened cleanly
- [x] Six websocket-relevant examples completed end-to-end against
production:
`13` (listen v1), `14` (listen v2), `15` (batch HTTP with
`diarize=True`),
        `21` and `24` (speak v1), `30` (agent v1)
  - [x] `ruff check` clean on touched files