Implement Rec - Phase 3 complete

.github/instructions/providers.instructions.md

@@ -31,9 +31,9 @@ Enforced by `tests/test_provider_boundaries.py`.
 
 ## Contract Surface
 
-- Every adapter satisfies the `TranscriptionProvider` protocol in `base.py`, including
-  `current_request_manifest` and `current_transport_evidence`, which exist so a *failed* call still
-  yields evidence.
+- Every adapter satisfies the `TranscriptionProvider` protocol in `base.py`. Failed-call evidence is
+  returned through the caller-owned `ProviderCallEvidence` sink passed to `transcribe()`, so
+  evidence stays scoped to one invocation instead of living on mutable adapter instance state.
 - `TranscriptionResult`, `RequestManifest`, and `TransportEvidence` are `extra="forbid"` and frozen.
   Add a field to the contract rather than smuggling data through an untyped dict.
 - Evidence contracts in `evidence.py` are versioned (`schema_name` + `schema_version`). A change to
@@ -51,6 +51,8 @@ wins if this file drifts from it.
 - Reset per-call capture state at the start of every call. Without it, a connection failure can
   attach the *previous* call's response as evidence for this one. Guarded by
   `tests/test_v42_evidence.py::test_openrouter_does_not_reuse_prior_response_on_connection_failure`.
+- Keep transport capture scoped to the call, not the adapter instance. Concurrent `transcribe()`
+  calls on one adapter must not be able to overwrite each other's response evidence.
 - Handle the streamed-body case (`httpx.ResponseNotRead`) rather than assuming `response.content`
   is always available.
 - When no response arrives — timeout, DNS, connection reset — emit