refactor(ui-react): split session list modules

[Astro-Han]

Summary

• split SessionListPanel into a small sidebar shell, session-sidebar-nav.tsx for the module nav/settings footer, and session-history-list.tsx for session groups, rows, row actions, status icons, and time buckets
• prune stale module-panel props from SessionListPanel; Skills, Automations, and Daily Review callbacks remain owned by ChatView, where those module panels are actually rendered
• remove the unreachable sessions module-nav branch; the new-task button still owns new-chat creation, and the three module nav buttons still select Daily Review, Skills, and Automations
• relax session-list contracts so they protect public props and rendered behavior without pinning the sidebar internals to three concrete source files or scanning the whole UI tree
• render SessionListPanel in contracts for OverlayScrollArea, time-bucket copy, and blocked-reason copy; row-action source contracts now resolve only the SessionHistoryList owner rendered by SessionListPanel
• remove an unnecessary !important from the palette input focus reset so the renderer important audit stays green

Scope

Part of #477.

This PR is structural only, not a visual redesign. The original #477 wording mentioned splitting session-list-panel.tsx into sessions / skills / plan reminders / daily review surfaces, but current main already renders those module panels through ChatView. The minimal correct PR6 is therefore to split the remaining sidebar owner into shell, nav/footer, and session-history modules, while removing now-dead module callback props from the sidebar contract.

Verification

• GREEN: npm run -w @maka/desktop build:main
• GREEN: node --test apps/desktop/dist/main/__tests__/session-list-public-contract.test.js apps/desktop/dist/main/__tests__/session-row-actions-fail-soft-contract.test.js apps/desktop/dist/main/__tests__/renderer-async-boundaries-contract.test.js apps/desktop/dist/main/__tests__/overlay-scrollbars-contract.test.js apps/desktop/dist/main/__tests__/search-modal-lifecycle-contract.test.js apps/desktop/dist/main/__tests__/daily-review-export-file-contract.test.js (34 passed)
• GREEN: npm run -w @maka/desktop test (1837 passed)
• GREEN: npm run -w @maka/desktop build:renderer (passes; existing Vite large chunk warning remains)

Commit Split

• fix(ui-css): remove palette input important reset
• refactor(ui-react): split session list modules
• refactor(ui-react): narrow session sidebar nav targets
• test(desktop): loosen session list contracts
• test(desktop): narrow session list contract sources