Activate proposal 0049 conformance fixtures 050-056

Adds harness support for the typed_event_collector directive introduced
by proposal 0049's seven conformance fixtures (050-056). The directive
declares one or more typed event collectors with optional filter_event_type
and include_caller_metadata flags; the parser aggregates the latter into
the provider's populate_caller_metadata kwarg.

Adds eight assertion shape handlers consumed by the fixtures:
contains_event, contains_exactly_one_event_of_type,
contains_event_of_type, contains_exactly_n_events_of_type,
does_not_contain_event_of_type, captured_event_field_values_cover,
every_captured_event_has, relative_order_of_events_matching. The
captured_event_field_values_cover shape uses set equality (matching
the spec text's "cover" semantic) rather than sorted-by-str (which
silently masks None-vs-primitive ordering ambiguity). An unknown-key
guard rejects fixture typos before any assertion runs.

Three graph builders cover the fixture topologies: a simple entry-ask-END
shape (050, 051, 052, 053, 056), a fan-out builder (054), and a
parallel-branches builder (055). The failure-path runner (053) sources
the calling-node NodeEvent from an unfiltered named collector when one
exists; otherwise attaches an AllEventsCollector specifically for that
assertion. The cause-chain walk handles the NodeException wrapper the
engine layers over the underlying ProviderUnavailable.

Adds tests/conformance/test_typed_event_harness.py with 31 unit tests
covering the harness helpers' edge cases: typo detection in assertion
keys, set-equality semantics, namespace tuple-vs-list normalization,
usage Mapping-vs-Usage comparison, cause-chain walking, populate_caller_metadata
aggregation, and the mock_model resolution. These would otherwise only
surface when a future fixture trips them.

Flips conformance.toml's [proposals."0049"] from not-yet to implemented
since 0.13.0. The leading-comment block notes that the OTel + Langfuse
observers continue driving their span / generation surface off the
sentinel NodeEvent pair during the dual-emit transition window;
type-discrimination migration of those observers waits on the
request-side-fields extension currently being drafted.

Author: chris-colinsky

conformance.toml

@@ -295,10 +295,19 @@ status = "implemented"
 since = "0.12.0"
 
 # Spec v0.41.0 (proposal 0049).  Typed LLM Completion Event — first
-# typed event variant on the observer event union.  Queued for
-# v0.13.0 alongside 0047.
+# typed event variant on the observer event union.  Shipped in
+# v0.13.0: provider dual-emits the typed event alongside the sentinel
+# NodeEvent pair (success-only per spec scope); LlmCompletionEvent
+# carries identity/scoping/outcome fields per the spec field table.
+# Conformance fixtures 050-056 activated by the typed_event_collector
+# harness directive.  The OTel + Langfuse observers continue to drive
+# their §5.5 / §8.4.4 surface off the sentinel NodeEvent pair during
+# the dual-emit transition window; type-discrimination migration
+# lands once the follow-on request-side-fields extension (proposal
+# 0057) ships.
 [proposals."0049"]
-status = "not-yet"
+status = "implemented"
+since = "0.13.0"
 
 # Spec v0.42.0 (proposal 0050).  Retry & degradation primitives —
 # failure-isolation middleware + call-level retry.  Queued for