release #5573: guard viewport anchor key against lone surrogates + CHANGELOG

CHANGELOG.md

@@ -14,6 +14,7 @@
 
 ### Fixed
 
+- **A message containing a broken emoji (lone Unicode surrogate) no longer breaks scroll position tracking.** If a message's text held a lone UTF-16 surrogate — e.g. a half-copied emoji from a truncated paste or interrupted stream — computing that message's scroll-anchor key threw an error, which broke scroll-position restore for the whole transcript. The anchor-key builder now handles lone surrogates safely (valid emoji are preserved; only the broken half is dropped), so scroll anchoring keeps working. Thanks @rumotoshino. (#5573, #5552)
 - **An in-progress CLI session now shows in the sidebar before its final output lands.** A CLI/agent session that had real activity (messages and user turns) but hadn't produced its final output yet was hidden from the sidebar until it completed, so an actively-running CLI session could be invisible while you waited on it. Such a session (real message count + user turns, not yet ended, no end reason) is now surfaced while it's still running. Empty/never-really-started rows stay hidden as before. Thanks @rodboev. (#5593, #5587)
 - **A completed answer is no longer followed by a misleading "No response from provider" card.** On the streaming settlement path, a stale terminal/partial-result flag could force the generic `no_response` error even when the current turn had already produced a full assistant answer — so you'd see the reply and then an error card under it. The generic silent-error path is now suppressed only when the merged current turn actually has a completed assistant answer; genuine failures (real silent failures, partial failures, auth/quota errors, cancellation, replayed rows, terminal tool/compression cases) all keep their existing error behavior. Thanks @rodboev. (#5592, #5575)
 - **The Mermaid diagram toolbar's "fit" and "fullscreen" buttons are now distinct icons.** The two buttons rendered a byte-identical glyph (the fullscreen icon was the fit icon's corner brackets drawn twice), so you couldn't tell them apart. Fullscreen now shows a distinct corner-frame-with-diagonal-arrows icon, visually separable from fit-to-screen's plain corner brackets. Thanks @rodboev. (#5565, #5525)