Subscriber unit test (10 cases):
- subscribed events
- main request emits duration + active count
- route template substitution (/api/items/{id})
- exception adds error.type attribute
- excluded paths emit nothing
- sub-requests emit nothing
- body size histograms from Content-Length headers
- no body metrics without Content-Length
- active_requests increments on request, decrements on finish
- reset clears cached meter and pending request state

BundleBootTest additions:
- http_server disabled by default when metrics are enabled
- http_server enabled registers the subscriber
- validation rejects metrics.http_server.enabled without metrics.enabled

- Extends the Metrics section with an HTTP Server table listing the four
  instruments emitted, their stability status and attribute sets.
- Updates the main config YAML block with metrics.http_server.enabled and
  metrics.http_server.excluded_paths.
- Notes that only main requests are measured; sub-requests are already
  covered by the main request duration.

Same issue as the metrics foundation fix: iterator_to_array() on PHP 8.1
requires a strict Traversable, but the OTel SDK types dataPoints as
iterable which can be either an array or a Traversable. The spread
operator [...$x] accepts both and works on PHP 8.1+.

Use FQCN per OTel semconv with a parent-class fallback for anonymous
classes, mirroring the messenger middleware fix.

…est.duration

The OTel SDK defaults are tuned for milliseconds and collapse all
sub-5s requests into the first bucket, making p95/p99 unusable.

…dling

Wrap each event listener's instrument calls in a swallowing try/catch
so that a broken meter provider cannot leak into Symfony's HttpKernel
flow. Track active_counted only when the counter increment succeeded
to keep up/down balance.

Replaces the inline anonymous-class fallback in the subscriber with
a reusable Util\ErrorTypeResolver, so the messenger middleware and
the HTTP client decorator can share the same canonical implementation.

Adds Configuration tests for the http_server.excluded_paths
normalization closure (mixed string/non-string entries, prepended
slash) and its default. Adds subscriber cases covering the data-null
short-circuits (every event firing on an untracked main request) and
extends the sub-request test to also exercise onRoute and onException.

…riber