Avoid .NET globalization crash in LLM benchmarks (#5335)

# Description of Changes

Sets `DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1` only on the benchmark
harness command that publishes generated C# modules. This keeps dotnet
startup out of localized DateTime/TimeZoneInfo formatting on the CI
runner, which was crashing before generated C# module publish could run.

Stacked on #5324.

```bash
gh workflow run llm-benchmark-periodic.yml \
  --repo ClockworkLabs/SpacetimeDB \
  --ref bot/debug-llm-csharp-publish \
  -f model_set=explicit \
  -f models="openrouter:openai/gpt-5.4-mini" \
  -f languages=rust,csharp,typescript \
  -f modes=guidelines \
  -f tasks=t_000_empty_reducers \
  -f dry_run=true
```

# API and ABI breaking changes

None.

# Expected complexity level and risk

1. CI benchmark harness environment fix.

# Testing

- [x] `cargo fmt --all`
- [x] `cargo check --manifest-path tools/xtask-llm-benchmark/Cargo.toml`
- [x] `ruby -e 'require "yaml";
YAML.load_file(".github/workflows/llm-benchmark-periodic.yml");
YAML.load_file(".github/workflows/llm-benchmark-validate-goldens.yml")'`\n-
[x] `git diff --check`

---------

Co-authored-by: clockwork-labs-bot <clockwork-labs-bot@users.noreply.github.com>

Author: clockwork-labs-bot

tools/xtask-llm-benchmark/src/bench/publishers.rs

@@ -330,6 +330,10 @@ impl DotnetPublisher {
     fn configure_dotnet_env(cmd: &mut Command) -> &mut Command {
         cmd.env("DOTNET_CLI_TELEMETRY_OPTOUT", "1")
             .env("DOTNET_NOLOGO", "1")
+            // The CI runner's .NET install can crash while formatting localized
+            // DateTime/TimeZoneInfo data before publish starts. Force invariant
+            // globalization so generated C# module publish reaches MSBuild.
+            .env("DOTNET_SYSTEM_GLOBALIZATION_INVARIANT", "1")
             // Prevent MSBuild node reuse issues that cause "Pipe is broken" errors
             // when running multiple dotnet builds in parallel.
             .env("MSBUILDDISABLENODEREUSE", "1")