* fix: address five AI quality findings
* fix: preserve search and session boundaries during reset
* fix: reset chat interaction and invalidate filtered search results
* fix: keep deep search diagnostics free of conversation content
* fix: preserve resume readiness and deep search result boundaries
* fix: show retryable search failures without logging model output
* fix: describe the background search model accurately
* docs: clarify deep search excerpt limits and data scope
* fix: keep search hydration diagnostics private
JATMN