Calm canary page chrome and assistant flows

Fix frontend shell persistence and modal semantics

Add guarded assistant concept fallback flow

Lock final workspace UI and guided flows

Polish non-rapid tabs and harden overflow rendering

chore: commit remaining UI polish, tests, and release gate artifacts

perf: optimize unified KB hot paths and UI session rendering

Fix unified KB routing, router RAG fallback, and table rendering

Redesign app tabs with Stitch-style shell and shared UI theme

Initial commit for HF deployment