Render agent host links in chat tool titles (#316804)

* Render agent host links in chat tool titles

Allow chat tool title markdown to preserve agent host links so empty remote file links can be converted into inline file widgets instead of being stripped by the generic markdown sanitizer.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Narrow agent host link rendering fix

Limit the chat-specific markdown options and file-widget pass to the input/output tool title path used by chat-confirmation-widget-title-inner.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Clarify chat query title test message

Update the regression test assertion message to match the chat query title scenario.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>