[joaquinbejar]

Codex review of #197 (two P2s) and of #195 (a nit).

• FIFO admission. With the ring full, a send already waiting could be overtaken forever by fresh sends that grabbed each freed slot first. A Logout could starve under sustained producers. A send now takes a slot from a tokio::sync::Semaphore with as many permits as the ring holds. The semaphore admits waiters in order, waits without allocating, and the receiver gives the permit back as it pops. close closes the semaphore, so waiting sends are refused.
• Drop drains. Dropping the receiver now drops what is still queued, one command at a time, each after the lock is released. A Connection that outlives the session keeps no command or pooled buffer alive.
• feat(core,tagvalue,engine): decode wide messages into lent field buffers (#77) #195 nit. The comment on FieldStore no longer claims the size is unchanged: the enum tag adds 8 bytes on aarch64 (840 to 848).

New unit tests:

• test_a_waiting_send_is_admitted_before_later_ones;
• test_dropping_the_receiver_drops_what_is_queued.

Both fail on the previous queue. The ready-gate allocation window stays at 0 blocks for 1024 sends.

cargo test --workspace --all-features: 2657 passed, 0 failed. fmt, clippy -D warnings, doc and check-spanish are clean. ADR-0008 updated.

Refs #76

[joaquinbejar]

APPROVE. Both PR197 findings are resolved. The original starvation and runtime shutdown buffer probes pass, alongside seven queue controls, four unchanged engine integration probes and ten authored queue tests. The allocation gate still measures zero blocks for 1024 ready gate sends. No new findings. Submitted as COMMENT because GitHub prevents the author account from approving its own pull request.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ironfix-engine/src/command_queue.rs	92.85%	1 Missing ⚠️

Files with missing lines	Coverage Δ
ironfix-core/src/message.rs	84.37% <ø> (ø)
ironfix-engine/src/command_queue.rs	87.27% <92.85%> (-1.79%)	⬇️

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