bench(compaction): bootstrap local Criterion harness + versioned JSON benchmark artifacts

[belveryin]

Closes #584

Summary

This PR delivers a baseline compaction benchmark infrastructure for local filesystem runs.

What changed

• Added Criterion bench target compaction_local.
• Implemented two deterministic scenarios: read_baseline and read_post_compaction.
• Added stable JSON artifact emission under target/tonbo-bench/ per run.
• Added versioned artifact fields for machine diffing: schema_version, resolved config, scenario id/name, throughput/latency summary.
• Refactored benchmark layout to Fusio-style split: benches/compaction/common.rs (shared logic) and benches/compaction_local.rs (scenario wiring).
• Fixed wasm test-target regression by target-gating Criterion to non-wasm dev-dependencies.
• Fixed key-space shaping bug by replacing rotate-based slot mapping with deterministic multiplicative hashing.
• Kept benchmark docs minimal in README.md with run commands + pointers to benchmark source files; removed docs/benchmarks/compaction-local.md.

Scope guarantees

• Criterion-based benchmark only.
• Local filesystem backend only.
• Env-only config (TONBO_COMPACTION_BENCH_*).
• No CI workflow changes.
• No rstest changes.
• No production runtime behavior changes.

How to run locally

TONBO_COMPACTION_BENCH_INGEST_BATCHES=768 \
TONBO_COMPACTION_BENCH_ROWS_PER_BATCH=96 \
TONBO_COMPACTION_BENCH_KEY_SPACE=4096 \
TONBO_COMPACTION_BENCH_ARTIFACT_ITERATIONS=64 \
TONBO_COMPACTION_BENCH_CRITERION_SAMPLE_SIZE=30 \
TONBO_COMPACTION_BENCH_WAL_SYNC=always \
cargo bench --bench compaction_local

Example artifact

• target/tonbo-bench/compaction_local-<run_id>.json
• Key fields: schema_version, config, scenarios[]

[ethe]

The overall direction looks good. The benchmark structure and versioned artifact output are useful. I do see one stability issue that should be fixed before merge.

[ethe]

A valid config can panic during scenario setup. TONBO_COMPACTION_BENCH_INGEST_BATCHES is parsed in here, but there is no > 0 validation. Later, latest_version_summary errors when list_versions(1) is empty (benches/ compaction/common.rs:429), and that bubbles into a panic at benches/compaction_local.rs:27.

[belveryin]

• Added explicit > 0 validation for TONBO_COMPACTION_BENCH_INGEST_BATCHES in benches/compaction/common.rs:102, so invalid config fails fast with BenchError::InvalidEnv.
• Kept the downstream guard in latest_version_summary (benches/compaction/common.rs:435) as defense-in-depth for unexpected empty version lists.