[Stephen Belanger (Qard)]

Remove delivery options that no longer affect behavior: checked_delivery, sync_flush (including its environment parser), enforce_queue_size_limit, and the former worker-channel queue_size. with_queue_max_size remains the actual bound on accepted writes, including in-flight work; new writes report Full at issuance when it is exhausted.

Remove the lazy client/span trigger_flush aliases and their private async port methods. Streaming requests the same nonblocking cutoff by dropping an eager flush() token. Callers that need the result await that token. Also delete the unused duplicate span-event merger from logger.rs; production normalization continues through SpanEventData.

Validation: 355 unit/integration tests and 10 doctests passed with all features, plus strict all-target Clippy, rustdoc, formatting and diff checks. Two obsolete option-only tests were removed. The retained capacity regression uses an explicitly selected runtime and still verifies immediate rejection. Existing delivery, failure-retirement, lifecycle and streaming tests pass.

Stacked on #136. The standalone uploader remains a compatibility delegate pending consumer migration during release preparation. Evaluator decomposition is the next stage. Planning documents remain excluded.