feat: criterion benchmarks proving primitive overhead is negligible

.hermes/plans/mytheclipse-round19-spec.md

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+# Implementation Spec: Round 19 — Criterion Benchmarks
+
+## Goal
+Buktikan klaim "secepat mungkin" (tujuan awal project) dengan benchmark
+nyata. Ukur overhead primitives race-safe vs baseline naif, supaya user
+tahu trade-off dan bisa memilih fitur dengan data.
+
+## New files
+
+### crates/mytheclipse/benches/primitives.rs
+Criterion bench untuk primitives core (feature `full`):
+- `parallel_map`: throughput 1000 item, concurrency 8 vs sequential loop
+  (pakai `black_box`)
+- `retry_ext`: overhead `.retry()` success-first vs 2 retries
+- `rate_limiter`: `RateLimiter::try_acquire` throughput (atomic CAS)
+- `semaphore_pool`: acquire/release cycle throughput — bukti no-leak + low
+  overhead
+- `aggregate_error`: `from_results` 1000 results all-ok vs 50% err
+- `shutdown_guard`: new + drop cost
+
+## Dependency
+- dev-deps: `criterion = "0.5"` + `[[bench]]` harness = false
+- `harness = false` di Cargo.toml bench section (criterion punya main sendiri)
+
+## Verification
+1. `cargo bench -p mytheclipse --bench primitives --all-features` — runs,
+   reports times
+2. `cargo build --workspace --all-features` — exit 0
+3. `cargo clippy --workspace --all-features` — 0 new warnings
+4. Spec + commit + push
+
+## Notes
+- Criterion 0.5 mendukung MSRV 1.60 — aman untuk rust-version 1.75.
+- Bench tidak jalan di CI (hanya manual) — tidak mempengaruhi pipeline.