refactor: migrate shell navigation to Astryx

[Astro-Han]

Summary

• Compose the Electron shell directly with Astryx AppShell and SideNav while preserving Maka's titlebar drag regions, resize/collapse behavior, routing, and narrow-window controls.
• Migrate chronological session navigation to Astryx List/Item and project navigation to TreeList, removing parallel arrow-key and expansion ownership. Session rename remains menu-owned and now contains Home/End/Arrow keys inside the editor.
• Reclassify the workspace workbar as Astryx TabList/Tab navigation while preserving dock persistence, browser keep-alive, disabled-state guards, and responsive right/bottom placement.
• Replace the drifting app-shell Storybook scaffold with the real shell composition and representative session/project fixtures. No shared Tabs/Item/Empty/Spinner barrel authority, Settings content, or Conversation composition is changed.

Verification

• npm run format:check
• npm run lint
• npm run typecheck
• npm test --workspace @maka/ui
• npm test --workspace @maka/desktop (2012 tests passed)
• npm test --workspace @maka/runtime (full suite passed, including the POSIX cancellation timing case)
• npm run build
• npm run build-storybook --workspace @maka/desktop
• npm run smoke:storybook --workspace @maka/desktop (27 renderer/play checks passed)
• npx playwright test --config e2e/playwright.config.ts e2e/project-management.spec.ts e2e/sidebar-geometry.spec.ts e2e/sidebar-navigation.spec.ts e2e/session-workbar.spec.ts e2e/topbar-overflow.spec.ts e2e/window-titlebar.spec.ts (13 passed)

Review focus

• Astryx owns generic shell/list/tree/tab interaction semantics; Maka continues to own product data, session identity, routing, persistence, Electron security, and window behavior.
• mobileNav.breakpoint is explicitly none: Astryx 0.1.9 otherwise applies its default responsive breakpoint even when mobileNav is false, which would bypass Maka's existing narrow sidebar controls.
• Workbar panels remain mounted and use hidden, preserving terminal/browser state when switching tabs.

[jackwener]

Superseded by #1732, which landed the same AppShell/SideNav, List/TreeList, workbar TabList, and real-shell Storybook migration from the same base, plus the follow-up focus/inset/E2E fixes. Rebasing this older alternate implementation would regress the merged official-shell result.