* fix(sidebar): increase virtualizer buffer for expanded parents
Fix#1530: archive sub-session layout broken because the virtualizer
used a fixed 28px height estimate per row. Expanded parents with inline
children are much taller. Now dynamically increases bufferSize when
expanded parents are present.
* fix(sidebar): correct expansion-key format for virtualizer buffer
The expansion key was using raw sessionId instead of the scoped format
'project:{archived|active}:{sessionId}'. This made hasExpandedParent
always false, so bufferSize never increased. Also removed dead
hasSessionSearchQuery branch.
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Co-authored-by: Leonid Skorobogatyy <bash@opencode.itc.local>
