Add BenchmarkDotNet coverage for enterprise integration and messaging patterns

[JerrettDavis]

Goal\nAdd fluent-vs-generated BenchmarkDotNet coverage for enterprise integration and messaging patterns.\n\n## Scope\nCover channels, filters, routers, translators, envelopes, message stores, outbox/idempotency, retry/reliability, scatter-gather, resequencer, wire tap, service activator, polling consumer, mailbox, and related catalog entries.\n\n## Acceptance criteria\n- Benchmarks use realistic payloads from production examples.\n- Fluent and generated routes are directly comparable.\n- Throughput, overhead, allocation, and retry/failure-path costs are represented where meaningful.\n- Reports use the shared markdown, CSV, and JSON exporters.

[JerrettDavis]

Matrix baseline landed in #338 / 86e5a59. The full published result matrix now lists every pattern route and every generator source in docs/guides/benchmark-results.md, with TinyBDD checks preventing docs drift. Leaving this issue open for the deeper production-scenario timing work requested here: family-specific scenario benchmarks with realistic payloads, direct fluent-vs-generated timing, and allocation/GC comparisons beyond the route-coverage matrix.

[JerrettDavis]

PR #340 landed on main as 20c840a with the first enterprise integration/messaging scenario benchmark batch.

Added dedicated BenchmarkDotNet fluent-vs-generated scenarios and published current-TFM results for:

• Message Routing: construction 23.42 ns / 224 B fluent vs 23.33 ns / 224 B generated; execution 707.34 ns / 4,744 B fluent vs 679.97 ns / 4,632 B generated.
• Message Translator: construction 39.49 ns / 424 B fluent vs 39.65 ns / 424 B generated; execution 365.30 ns / 2,528 B fluent vs 381.79 ns / 2,528 B generated.
• Service Activator: construction 4.825 ns / 32 B fluent vs 4.641 ns / 32 B generated; execution 25.48 ns / 256 B fluent vs 26.49 ns / 256 B generated.
• Reliability Pipeline: construction 34.90 ns / 392 B fluent vs 33.16 ns / 328 B generated; execution 2.303 us / 3,992 B fluent vs 381.36 ns / 1,872 B generated.

Docs updated in README, docs/guides/benchmarks.md, and docs/guides/benchmark-results.md. Local validation and PR/main checks are green, including CI, Publish docs, CodeQL, and Codecov. Leaving this issue open for the remaining enterprise integration/messaging patterns.