* fix: stabilize telegram draft stream message boundaries
* fix: suppress NO_REPLY lead-fragment leaks
* fix: keep underscore guard for non-NO_REPLY prefixes
* fix: skip assistant-start rotation only after real lane rotation
* fix: preserve finalized state when pre-rotation does not force
* fix: reset finalized preview state on message-start boundary
* fix: document Telegram draft boundary + NO_REPLY reliability updates (#33169) (thanks @obviyus)
When enforceFinalTag is active (Google providers), stripBlockTags
correctly returns empty for text without <final> tags. However, the
handleMessageEnd fallback recovered raw text, bypassing this protection
and leaking internal reasoning (e.g. "**Applying single-bot mention
rule**NO_REPLY") to Discord.
Guard the fallback with enforceFinalTag check: if the provider is
supposed to use <final> tags and none were seen, the text is treated
as leaked reasoning and suppressed.
Also harden stripSilentToken regex to allow bold markdown (**) as
separator before NO_REPLY, matching the pattern Gemini Flash Lite
produces.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The suffix regex matched NO_REPLY at the end of any response,
suppressing substantive replies when models (e.g. Gemini 3 Pro)
appended NO_REPLY to real content.
Replace prefix+suffix regexes with a single whole-string match.
Only responses that are entirely the silent token (with optional
whitespace) are now suppressed.
Add unit tests for the fix.
Fixes#19537
