Two data-integrity blockers from round-3 review (nesquena-hermes 2026-09-19):
1. [CORE] A successful /compress returns the full transcript, but
_applyManualCompressionResult kept the bounded preflight's paging
signals (_messagesTruncated/_oldestIdx). Render now restores them
before renderMessages(), same ordering as settle/cancel paths.
2. [SILENT] _restoreSettledSession preservation used
(prefix || suffix), so repeated identical turns (colliding
_messageIdentityKey) made BOTH comparisons succeed and the prefix
branch spliced at the wrong offset - silently dropping rows and
duplicating others. The server truncation signal now decides the
strategy: truncated => suffix-exclusive, untruncated => prefix.
Tests: node behavioral driver covering /compress paging restore,
repeated-turn settle (no drop/dup, authoritative offset), and
gap-free msg_before paging after bounded recovery.
