Merge train: #9654 #9635 (fs ordering, Bun TCP facades)

[proggeramlug]

Lands #9654 (async fs write-unlink ordering preserved, #9574) and #9635 (Bun listen/connect TCP + Unix socket facades over the existing external node:net transport).

#9635 was the one PR today that needed real hand-merging — ten conflicts, three of which no mechanical rule resolves:

• adopt.rs — main had refactored to match &transport { Transport::Plain(stream) => … } while this PR still used a bare stream and needed a new remote binding. Either side alone was wrong; remote is now computed through the new transport match.
• lib.rs — one conflict was purely positional: git aligned the mod socket_events; split (from the compat(claude): provide Bun.ant host hooks #9633 train) against this PR's inline copies of the functions that split had moved. Verified this PR does not modify those functions — its lib.rs changes are remote_addr plumbing plus mod bun_tcp; — before taking the split side, and confirmed mod bun_tcp; still lands.
• dispatch_a_c.rs — both sides were complete match arms sharing a trailing }\n}, so concatenation produced an unclosed delimiter. Bridged so the serve arm closes before listen/connect opens.

Verified the merge lost nothing: bun_tcp.rs is byte-identical to the PR's own copy except the dead-code annotation below, and call-site counts for every helper match.

Gate fixes carried:

• Root-holder verdicts for TOKENS (write-token to socket HANDLE id — the same handle-band ids ABORTS already carries) and NEXT_TOKEN (a counter).
• build_error_object held two freshly allocated JsStrings across field writes. JsString is a bare pointer wrapper, and the function already had a TransientRootScope for its receiver, so the strings are now rooted through it.
• Module-level allow(dead_code) on bun_tcp.rs: several helpers and two BunSocket fields are written but not yet read on this build. Flagging for the author — they are reachable only from paths a follow-up turns on, and deleting them would also remove the writes that feed them.

Validation: run_lint_gates.sh all 62 gates pass; release build green; RUST_TEST_THREADS=1 perry-runtime 3064/0; manifest_consistency 5/5.

Rebase-merge preserving authorship.