- Add SyncWriter to synchronize stdout/stderr writes with prompts
- Add promptMutex to serialize interactive prompts
- Keep rawStdout/rawStderr for BubbleTea to avoid deadlock
- Update test Taskfile with nested deps scenario
Add support for interactive variable prompting using Bubble Tea.
Variables can be marked as `interactive: true` in the requires section,
and users will be prompted to enter values for missing variables when
running in a TTY.
Features:
- New `interactive` field on required variables
- Bubble Tea-based text input and select prompts
- --no-tty flag to disable interactive prompts
- Automatic skip when variable is already set
