feat: add git worktree session support with improved UI

Implement comprehensive worktree session support allowing users to spawn sessions in temporary git worktrees. Includes backend worktree management, full-stack integration, and refined UI for session type selection.

Backend:
- Add worktree creation/removal utilities with branch management
- Track worktree metadata (basePath, branch, name, path) in session metadata
- Automatic cleanup of worktrees when sessions fail or exit
- Enhanced error handling with stderr tail logging

UI improvements:
- Redesign session type toggle with improved alignment and spacing
- Move worktree description inline with label for cleaner layout
- Add branch name input field that appears when worktree mode selected
- Auto-focus on worktree input when switching modes
- Reduce gap between radio options from gap-3 to gap-1.5
- Update descriptive text and placeholders for clarity

Integration:
- Thread worktree parameters through API client, RPC handlers, and daemon
- Add worktreeEnv utility to read worktree info from environment
- Update session spawning to support both simple and worktree modes

cli/src/api/rpc/RpcHandlerManager.ts

@@ -51,7 +51,10 @@ export class RpcHandlerManager {
             const result = await handler(params as any)
             return JSON.stringify(result)
         } catch (error) {
-            this.logger('[RPC] [ERROR] Error handling request', { error })
+            const details = error instanceof Error
+                ? { message: error.message, stack: error.stack }
+                : { error: String(error) }
+            this.logger('[RPC] [ERROR] Error handling request', details)
             return JSON.stringify({
                 error: error instanceof Error ? error.message : 'Unknown error'
             })
@@ -91,4 +94,3 @@ export class RpcHandlerManager {
 export function createRpcHandlerManager(config: RpcHandlerConfig): RpcHandlerManager {
     return new RpcHandlerManager(config)
 }
-