docs: document resource detectors and Sentry profiling on free-threaded CPython

[lesnik512]

Closes #181. Docs plus pinning tests; no change under lite_bootstrap/.

Resource detectors

New ### Resource subsection under OpenTelemetry. OpenTelemetryInstrument builds its resource with Resource.create, so OTEL_EXPERIMENTAL_RESOURCE_DETECTORS and OTEL_RESOURCE_ATTRIBUTES already work. The configured attributes merge last.

The issue said lite-bootstrap's service_name overrides OTEL_SERVICE_NAME. It's stronger than that: service_name defaults to "micro-service", so OTEL_SERVICE_NAME is overridden unless service_name is empty. The docs say so.

The example lists detectors explicitly and doesn't mention *. The wildcard doesn't exist in opentelemetry-sdk 1.28, our floor. I checked 1.28's Resource.create: process, os and host are registered there, and explicit attributes still merge last.

New tests in tests/instruments/test_opentelemetry_instrument.py:

• test_opentelemetry_configured_service_name_wins_over_env pins service.name with OTEL_SERVICE_NAME set, for three configs: the default, service_name, and opentelemetry_service_name.
• test_opentelemetry_resource_detectors_enrich_resource checks that the process detector and OTEL_RESOURCE_ATTRIBUTES both reach the resource.

Profiling on free-threaded CPython

The Pyroscope section now says the extra can't install on free-threaded CPython (#171) and points to Sentry continuous profiling through sentry_additional_params.

The brief required this to be checked before it was documented. I ran it on CPython 3.14.7t, GIL disabled, with sentry-sdk 2.71.0 installed via lite-bootstrap[sentry]:

• Setup: FreeBootstrapper with profile_session_sample_rate=1.0 and profile_lifecycle="manual", then start_profiler(), 1.5 s of CPU work on 5 threads, and stop_profiler().
• A capturing Transport received one profile_chunk envelope with 777 samples across 6 thread ids.
• sys._is_gil_enabled() was still False afterwards, and nothing warned under -X dev.

Only the manual lifecycle was exercised, so that's the one the docs example uses.

Checks

just lint-ci, just test-ci (340 passed, 100% coverage), just docs-build (strict), and just adr-check all pass.