removeAllDetails() uses replaceOutsideCode() which splits content on
triple-backtick code blocks before applying the details-removal regex.
When thinking/reasoning content inside a <details> block contained
code blocks (backticks survive html.escape), the <details> opening
and </details> closing tags ended up in different split segments,
making the regex unable to match either. This caused thinking content
to leak through to TTS playback.
Fix: add a direct <details> strip (without code-block splitting) as
the first step of getMessageContentParts(), which is the TTS-specific
entry point. This catches the edge case while keeping removeAllDetails
safe for copy-to-clipboard (where legitimate <details> inside code
blocks should be preserved).
Fixes#22197