Rename CLI from 'think' to 'thought' and add stream command
- Rename main binary from 'think' to 'thought'
- Add 'thought stream' subcommand (replaces 'thought interactive --tui')
- Update all references and help text to use 'thought'
- Remove separate thought.rs binary in favor of single unified CLI
- Update README to reflect new command structure
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Co-Authored-By: Claude <noreply@anthropic.com>