docs: add benchmark results to README

- cosmo-benchmark/README.md: add Latest Results section with actual
  numbers from latest run (20 iter, 46-row table, Apple Silicon)
- README.md: add Benchmarks section with head-to-head comparison table
  linking to cosmo-benchmark/

CosmoSQL (NIO) is 1.7× faster than FreeTDS on warm queries.
decode<T>() and toJson() are NIO-only features at ~1.5 ms.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: vkuttyp

README.md

@@ -1078,6 +1078,23 @@ swift test
 
 ---
 
+## Benchmarks
+
+> CosmoSQLClient (NIO) vs SQLClient-Swift (FreeTDS) · macOS · Apple Silicon · MSSQL Server 2019  
+> Table: 46 rows × 20 columns · 20 iterations per scenario
+
+| Scenario | CosmoSQL (NIO) | FreeTDS | Winner |
+|---|---|---|---|
+| Cold connect + query + close | 14.30 ms | 13.92 ms | ≈ tie |
+| Warm full-table query | **0.95 ms** | 1.58 ms | 🔵 **1.7× faster** |
+| Warm single-row query | **0.64 ms** | 1.10 ms | 🔵 **1.7× faster** |
+| Warm `decode<T>()` (Codable) | 1.53 ms | N/A | 🔵 only |
+| Warm `toJson()` | 1.56 ms | N/A | 🔵 only |
+
+Run the benchmarks yourself — see [`cosmo-benchmark/`](cosmo-benchmark/).
+
+---
+
 ## Related Projects
 
 - [SQLClient-Swift](https://github.com/vkuttyp/SQLClient-Swift) — The original MSSQL driver using FreeTDS (predecessor to this package)

cosmo-benchmark/README.md

@@ -28,6 +28,34 @@ BENCH_USER=sa BENCH_PASS=mypass BENCH_ITER=50 \
 swift run -c release
 ```
 
+## Latest Results
+
+> Environment: macOS, Apple Silicon, frpc tunnel → MSSQL Server 2019  
+> Table: `Accounts` (46 rows × 20 columns) · 20 iterations per scenario
+
+```
+🔵  CosmoSQLClient (NIO-based, pure Swift)
+  Cold  connect + query + close      avg  14.30 ms  min  10.84 ms  max  44.55 ms
+  Warm  query only (persistent conn) avg   0.95 ms  min   0.74 ms  max   1.23 ms
+  Warm  single-row query             avg   0.64 ms  min   0.47 ms  max   1.80 ms
+  Warm  query + decode<Account>()    avg   1.53 ms  min   1.25 ms  max   2.36 ms
+  Warm  query + toJson()             avg   1.56 ms  min   1.33 ms  max   2.83 ms
+
+🟠  SQLClient-Swift (FreeTDS-based)
+  Cold  connect + query + disconnect avg  13.92 ms  min  11.06 ms  max  20.54 ms
+  Warm  query only (persistent conn) avg   1.58 ms  min   1.17 ms  max   4.03 ms
+  Warm  single-row query             avg   1.10 ms  min   0.91 ms  max   2.41 ms
+```
+
+### Head-to-head (warm queries)
+
+| Scenario | CosmoSQL (NIO) | FreeTDS | Winner |
+|---|---|---|---|
+| Warm full-table query | **0.95 ms** | 1.58 ms | 🔵 **1.7× faster** |
+| Warm single-row query | **0.64 ms** | 1.10 ms | 🔵 **1.7× faster** |
+| `decode<T>()` (Codable) | 1.53 ms | N/A | 🔵 only |
+| `toJson()` | 1.56 ms | N/A | 🔵 only |
+
 ## Scenarios
 
 | Scenario | CosmoSQL (NIO) | FreeTDS |