feat(testing): configure ignored routes in test server

[hugosmoreira]

Summary

• add an optional TestServerOptions bag to getTestServer
• pass ignoredRoutes through while preserving the existing default behavior
• document disabling the default favicon and robots.txt short-circuit
• test defaults, both ignored paths, empty/whitespace and custom overrides, error propagation, and the installed public /testing entry point

Fixes #778

Validation

Local verification on Windows with Node 22.22.1 (generated API docs checked separately with Node 24.18.0):

• npm test -- --reporter dot: 126 passing, including 24 HTTP integration cases and two pack-and-install tests
• identical 25-case HTTP contract: 17 passing / 8 expected failures on the unchanged parent, all 25 passing with this feature
• negative control in an isolated checkout: bypassing the ignoredRoutes pass-through causes eight HTTP cases and the new installed-package test to fail as expected
• packed CommonJS and ESM runtime consumers pass
• exported TestServerOptions declaration checks pass with strict TypeScript 5.8.2, both Node16 and legacy Node10 module resolution, without skipLibCheck
• npm run check, compilation, changed-file ESLint/Prettier, and git diff --check pass; lint has one unchanged unused-generic warning also present on the parent
• npm run docs passes and generated documentation is unchanged
• all six non-Docker conformance groups pass using the workflow's pinned v1.8.3 client: legacy HTTP/event/CloudEvent, declarative HTTP/CloudEvent, and HTTP concurrency

Conformance used the same framework CLI directly on Windows to avoid an npm wrapper process; it was not a hosted Linux workflow run. The hosted OS/Node matrix and buildpack checks remain pending; the seven failure-labelled verification workflows on the previous revision expired awaiting approval without executing jobs.

[hugosmoreira]

I've added regression coverage for both ignored routes, default/empty/custom options, error propagation, and the installed public /testing entry point. This follow-up changes tests only.

The full suite passes locally: 126 tests on Windows with Node 22.22.1. The new cases fail as expected when the option pass-through is bypassed. Packed CommonJS/ESM consumers, strict TypeScript declaration checks, lint/build/docs, and all six non-Docker conformance groups also pass. I've updated the PR description with the verification details and environments.

The seven failure-labelled verification workflow runs on the previous revision expired awaiting approval and had no jobs. Could a maintainer approve/rerun the checks for this update? The hosted OS/Node matrix and buildpack checks still need to run.