fix: surface worktree hook failures

[kbwo]

Summary

• surface pre-creation and post-creation hook failures in a dedicated TUI error screen
• preserve hook stdout/stderr in ProcessError and logs
• keep post-creation worktree creation successful while blocking auto session start until the error is acknowledged

Verification

• bun run typecheck
• bun run lint
• bun run build
• bun run vitest --run src/components/App.test.tsx src/utils/hookExecutor.test.ts src/services/worktreeService.test.ts

Note: full bun run test was attempted, but an existing dist submodule test failed while running git config --global protocol.file.allow always because /Users/kbwo/.gitconfig was locked. The targeted tests for this change pass.