feat: implement worktree session creation and management

- Added `createWorktreeSession` utility to handle the creation of new sessions with auto-generated worktrees.
- Introduced branch name generation utilities for creating unique and friendly branch names.
- Updated `CommandPalette` to trigger worktree session creation via a command.
- Refactored keyboard shortcuts to support new worktree session creation with Shift + Cmd/Ctrl + N.
- Enhanced project settings to include worktree defaults (branch prefix, base branch, auto-create option).
- Updated persistence logic to preserve worktree defaults when saving project settings.
- Modified menu actions to initiate new worktree sessions.
- Ensured proper handling of existing branches to avoid conflicts during worktree creation.

packages/ui/src/lib/api/types.ts

@@ -334,12 +334,19 @@ export interface FilesAPI {
   execCommands?(commands: string[], cwd: string): Promise<{ success: boolean; results: CommandExecResult[] }>;
 }
 
+export interface WorktreeDefaults {
+  branchPrefix?: string;        // e.g. "feature", "bugfix" (no trailing slash)
+  baseBranch?: string;          // e.g. "main", "develop", or "HEAD"
+  autoCreateWorktree?: boolean; // future: skip dialog, create worktree automatically
+}
+
 export interface ProjectEntry {
   id: string;
   path: string;
   label?: string;
   addedAt?: number;
   lastOpenedAt?: number;
+  worktreeDefaults?: WorktreeDefaults;
 }
 
 export interface SettingsPayload {