Enhance session sidebar with PR worktree support (#342)

* feat: refactored sessions sidebar to be workspaces centric

- Add createWorktreeOnly helper and status checks
- Add createWorktreeOnly to create a standalone worktree for the active project
- Show error toasts when no active project or not a Git repository
- Refresh session list and show success toast with created worktree details

* feat: show attention indicator and status marker in SessionSidebar

- Show unread attention indicator for sessions with pending updates
- Display status marker combining streaming and unread indicators in the session row
- Introduce attention diamond pulse animation and associated CSS for the new indicator

* fix(SessionSidebar): reserve header actions space when repo state is known

* chore(doc): add PR status colors to custom themes

packages/ui/src/lib/theme/themes/presets.ts

@@ -1,4 +1,5 @@
 import type { Theme } from '@/types/theme';
+import { withPrColors } from './prColors';
 
 import aura_dark_Raw from './aura-dark.json';
 import aura_light_Raw from './aura-light.json';
@@ -70,4 +71,4 @@ export const presetThemes: Theme[] = [
   mono_light_Raw as Theme,
   vitesse_dark_dark_Raw as Theme,
   vitesse_light_light_Raw as Theme,
-];
+].map((theme) => withPrColors(theme));