* fix(telegram): enable HTML formatting for model switch messages
The model switch confirmation message was displaying raw Markdown
(**text**) instead of bold formatting because parse_mode was not set.
Changes:
- Add optional extra parameter to editMessageWithButtons for parse_mode
- Change format from Markdown ** to HTML <b> tags
- Pass parse_mode: 'HTML' when editing model switch message
Fixes the issue where model names appeared as **provider/model**
instead of bold text in Telegram.
* fix(telegram): escape HTML entities in model switch confirmation
Add defensive `escapeHtml` helper to sanitize `selection.provider`
and `selection.model` before interpolating them into the HTML
callback message. This prevents potential API rejection (HTTP 400)
if future provider or model names contain `<`, `>`, or `&`.
Addresses review feedback on unescaped HTML interpolation.
* test(telegram): cover HTML model switch confirmation
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Co-authored-by: Frank Yang <frank.ekn@gmail.com>
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