feat(tui): autocomplete cd directories - #41870

Summary

• switch /cd from command completion to directory completion after its argument separator
• list immediate child directories with shell-style current, home, parent, nested, and absolute path handling
• persist project-scoped /cd recents and expose them as prioritized supplemental options
• add generic two-step destructive actions for autocomplete options

Test plan

• bun typecheck in packages/tui
• bun typecheck in packages/plugin
• bun test --timeout 30000 --only-failures in packages/tui (639 pass, 5 skip)
• bun test test/prompt/autocomplete.test.ts in packages/tui
• isolated opencode-drive coverage for immediate directory-only listing, nested traversal, /cd persistence, recent ordering, and Ctrl+D removal