Improve Runtime Console workspace navigation

[yyjeqhc]

Summary

• make each selected workspace independently collapsible while keeping the selected Session and composer state intact
• add loaded-Session and retained-message filtering, clearer ACK/resolution presentation, and a latest Agent message context card
• dock the Context panel from 1280px with a wider reading rail and keep tracked dist assets synchronized
• preserve bounded Session-list total/truncated metadata across local search, selection, and language rerenders

Validation

• cd frontend && npm test — 88 passed
• cd frontend && npm run typecheck
• cd frontend && npm run check:dist
• git diff --check

No backend API, authority, Workflow Session identity, or mutation semantics are changed.