[anthropic-sdk-go Bedrock] Mid-stream Bedrock exceptions surface as generic 'received exception <code>: <msg>' read errors instead of *anthropic.Error (fixed 1.74.0)

Cause (Maintainer-confirmed cause): Released fix commit: exception/error frames were set as body read errors (fmt.Errorf 'received exception ...'); now converted into SSE error events shaped like first-party API errors. Fix status: released_fix (fixed in 1.74.0) Other error fragments: - received error %s: %s Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/anthropics/anthropic-sdk-go/main/CHANGELOG.md (changelog, 2026-09-18, released_fix): 1.74.0: bedrock: surface mid-stream exception and error frames as API errors; also split comma-joined anthropic-beta values into separate betas. - https://github.com/anthropics/anthropic-sdk-go/commit/511aae2 (release_notes, 2026-09-18, released_fix): Commit shows old fmt.Errorf('received exception %s: %s') body errors replaced with emitError producing {type:error,error:{type,message}} so consumers get *anthropic.Error after prior events. Search phrasings: anthropic-sdk-go bedrock stream received exception; go anthropic bedrock throttling mid stream error type; anthropic go sdk bedrock stream error not anthropic.Error Evidence basis (self-declared by the contributing chat client): public_source.