bench-read-bulk driver: invoke .NET in -c Release and Rust in --release

Rust''s debug profile costs the bench ~45% of solo throughput and ~3x of
p99 latency vs release (267 vs 184 solo calls/sec, p99 5.7 vs 16ms).
Debug disables inlining, runs overflow checks on every arithmetic op,
keeps Future state machines un-collapsed, and lets every Vec allocation
through unoptimized. Other compiled clients in the matrix don''t see
this gap: Go always builds optimized, Python is interpreted, and the
JIT-tiered runtimes (HotSpot for Java, CoreCLR Tier 1 for .NET) close
most of the gap during the warmup window.

The driver now requests `cargo run --release` for Rust and `dotnet run
-c Release --no-build` for .NET, so the two compiled-AOT clients race
under their production-equivalent profiles. Callers must `cargo build
--release -p mxgw-cli` and `dotnet build ... -c Release` once before
running the bench; `--no-build` then keeps each measurement window
free of compilation overhead.

Live re-run (5-way concurrent, 30s, bulkSize 6) after the switch:
  rust:  145.35 calls/sec (was 123.26 in debug; 18% gain under contention)
  go:    185.59 calls/sec
  java:  171.80 calls/sec
  dotnet:172.31 calls/sec
  python:140.52 calls/sec

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/bench-read-bulk.ps1

@@ -126,8 +126,13 @@ function Get-ClientCommand {
 
     switch ($Client) {
         "dotnet" {
+            # -c Release matches the rest of the matrix: HotSpot/Tier 1 JIT
+            # closes most of the debug/release gap for .NET on its own, but
+            # Release also disables JIT inline thresholds that hurt Stopwatch-
+            # bracketed measurement noise. Same project must have been built
+            # in Release at least once before this --no-build invocation.
             $cliArgs = @(
-                "run", "--project", "clients/dotnet/MxGateway.Client.Cli", "--no-build", "--",
+                "run", "--project", "clients/dotnet/MxGateway.Client.Cli", "-c", "Release", "--no-build", "--",
                 "bench-read-bulk",
                 "--endpoint", $httpEndpoint,
                 "--api-key-env", $ApiKeyEnv,
@@ -163,8 +168,13 @@ function Get-ClientCommand {
             return [pscustomobject]@{ file = "go"; args = $cliArgs; cwd = (Join-Path $repoRoot "clients/go") }
         }
         "rust" {
+            # --release is essential: Rust debug builds disable inlining and
+            # add overflow checks, which costs the bench ~45% of throughput
+            # and ~3x of p99 latency vs release. The other compiled clients
+            # don't have this gap (go run is optimized, dotnet/java run JIT-
+            # optimized after the warmup window).
             $cliArgs = @(
-                "run", "--quiet", "-p", "mxgw-cli", "--",
+                "run", "--release", "--quiet", "-p", "mxgw-cli", "--",
                 "bench-read-bulk",
                 "--endpoint", $httpEndpoint,
                 "--api-key-env", $ApiKeyEnv,