Improve session traceability UI experience

[yycn012345-cpu]

Background

The Session Traceability page is a core audit workflow for reviewing session chains, timeline context, risk signals, and detailed evidence. The current experience can be improved for faster investigation and clearer operational judgment.

Scope

• Review the existing Session Traceability / Session Audit UI flow.
• Improve information hierarchy, scanability, and navigation between session list, timeline, details, and risk evidence.
• Keep the implementation consistent with the existing frontend architecture, locale system, and design conventions.
• Preserve current data contracts unless a change is explicitly required.

Acceptance Criteria

• The page presents key session context and risk evidence more clearly.
• Common investigation actions are easier to discover and use.
• UI states for loading, empty data, errors, and dense content remain polished.
• The work is verified locally with the project’s available checks.