Fix search result navigation and highlight reliability across long conversations

[samhu1]

Problem

Search currently returns session and message hits, but navigating from a result into a long conversation can be unreliable. In long threads, the target message may not scroll into the expected position, the highlight may be easy to miss, or the user may lose context after jumping between multiple results.

Why this matters

Search only pays off if result navigation is trustworthy. Weak jump-to-result behavior makes the feature feel approximate rather than precise, especially for users debugging older conversations or tracing file-edit history.

Acceptance Criteria

• Clicking a search hit should consistently focus the correct session and target message.
• The highlighted result should remain visually obvious long enough for the user to orient themselves.
• Repeated navigation between results in the same session should not leave stale highlights behind.
• Long conversations and compact layouts should still land on the intended message reliably.
• Add a deterministic repro scenario or automated coverage for long-session navigation behavior.

[shaishab316]

Hey, I'd like to take a look at this. Can you point me to the search navigation code — is it under src/ in the chat or workspace module?