Release main-1401c2e

feat: add --fetch flag for direct benchmark suite download (#26)

## Summary        
- Add `--fetch <url>` flag to `run` subcommand that downloads a
`.tar.zst` benchmark suite, extracts it to a
- Streaming decompression (no disk buffering of the archive — memory
efficient)
- Auto-detect single-subdirectory wrapping (handles archives that wrap
content in a subdirectory)
- Mutually exclusive with `--data-dir` (conflicts_with enforced by clap)
- 3 unit tests covering flat extraction, subdirectory extraction, and
bad URL rejection
 - Clippy clean, all tests pass             
                                                                       
Closes #14 

## Test Plan
- [x] `cargo test -p bento-bench` — 3/3 pass
- [x] `cargo clippy -p bento-bench -- -D warnings` — zero warnings
- [ ] Manual end-to-end: `bento-bench run --fetch <real-url>
--iterations 1`

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Co-authored-by: zeroklaw <267418690+zeroklaw@users.noreply.github.com>