fix(desktop): refresh session model metadata on switch

[OmarB97]

Summary

• Cache desktop session runtime metadata per session, including model, provider, reasoning effort, service tier, fast mode, personality, and yolo state.
• Mirror the focused session's cached runtime metadata into the statusbar immediately when switching sessions.
• Prevent background session.info updates from clobbering the foreground UI while still keeping each session cache fresh.
• Clear stale model/effort/provider/fast state on cold resumes until the gateway returns exact runtime info.

Repair note

This upstream PR branch was replaced with a clean upstream/main cherry-pick after the earlier fork-sync branch became polluted/conflicting. The current head is 579c67dcfaa7b94f071ba8dd4bdb99a2ff9c89ec; the PR is mergeable and its diff is limited to the six desktop runtime-metadata files.

Verification

• npm ci --workspace apps/desktop
• npm --prefix apps/desktop run typecheck
• cd apps/desktop && npx vitest run --environment jsdom src/app/session/hooks/use-session-state-cache.test.tsx
• git diff --check upstream/main..HEAD

Notes: the vitest command passes 1 file / 5 tests. npm ci reports the existing Node engine warning for @icons-pack/react-simple-icons under Node v22.22.3. No screenshot/video is attached because this changes session-scoped state hydration for existing statusbar controls, not visual layout, styling, or labels.