Refactor workspace routing, controllers, and styling

[jialudev]

Summary

This PR contains four workspace web updates:

1. Make workspace navigation router-first.

   • Derive the active workspace pane and sidebar tab from the current React Router location instead of duplicating that state in Zustand.
   • Route pane selections through pathForPane and React Router navigation so deep links, aliases, and browser back/forward behavior stay consistent.
   • Add focused navigation tests and document the router-first maintenance rules in the web architecture and development docs.

2. Split the workspace controller into focused hooks.

   • Keep useWorkspaceController as the composition layer for WorkspacePage.
   • Move conversation, agent, upgrade, profile preview, Hub, and shell behavior into dedicated controller hooks with shared TypeScript contracts.
   • Add stronger types for workspace query setters, navigation inputs, controller props, and agent-like data used by the workspace UI.

3. Reorganize workspace styling and theme tokens.

   • Move large workspace styles out of global CSS and into the relevant workspace, sidebar, modal, conversation, agent, and Hub component stylesheets.
   • Refresh light/dark theme tokens, typography, borders, shadows, focus states, and Hub workspace variables for more consistent theming.
   • Keep message content and workspace component styling aligned with the updated token set.

4. Remove legacy static frontend assets.

   • Delete the old web/static comparison assets now that the Vite app is the maintained frontend.
   • Update workspace and web documentation to describe the current web/app to web/static-dist build flow.

Testing

• Not run by Codex, per request. The branch was already tested locally.