Introduce workspace bootstrap and thread hydrate JSON-RPC methods and related schema changes (generated types + new schema.workspace.ts). Update server routes and schema usages. Improve desktop UX and compatibility: hydratePersistedDesktopState now migrates legacy a2ui flags to desktopFeatureFlagOverrides, CodeFilePreview caps line numbers (10k) and shows an ellipsis, and Sidebar ignores drag starts from interactive elements, adds stable handlers for workspace open state & thread selection, and wires up reorder keyboard handling (covered by a new test). Misc server/session/test updates to reflect these changes.
