Temporal, streams, and QUIC get major fixes

Temporal can now build with system ICU (bba3422, c4c1163, 9800c29)

Node now enables V8 Temporal support even when using a shared/system ICU, removing the earlier build-time disablement and wiring in the new v8_enable_temporal_systemicu flag. This unblocks Temporal for more build configurations and avoids depending on ICU internal headers.

stream/iter gets a major behavior and API polish pass (04f1b72, 8fc9838, fe1a203, 0d4a844, 847da07, bf4bd44, fc78459, 2964712)

The classic stream/iter adapters were refactored to fix backpressure, cancellation, wakeup, and writable lifecycle edge cases, with matching documentation updates. The changes tighten semantics for fromReadable(), fromWritable(), and toWritable(), and the expanded tests cover previously shaky interop paths.

QUIC writer backpressure and abort handling are corrected (fe1a203)

QUIC stream writers now track a single pending write, enforce strict backpressure more accurately, and support abort-aware waiting for drain. That makes write ordering and rejection behavior more predictable under load.

FFI now avoids undefined behavior on zero-length null-pointer copies (24b9ca9)

The FFI helpers skip memcpy() when the length is zero, which fixes UB when callers pass a null pointer with an empty transfer. A new test locks in the safe zero-length behavior across buffer and array buffer paths.

Other misc changes

• process.ref() / process.unref() graduated from experimental (f950eb8)
• Trace events tests were reworked for perfetto support (e7d8ab5)
• CI label/workflow and collaborator-guide updates for resume-ci handling (bd111f3, 6825d88)
• Alpine docs updated to tier 2 / minimum 3.21 (bcf5850)
• test-fs-rm now accepts libc++’s ENOTEMPTY on POSIX (72bb834)
• Minor doc cleanup for util.markPromiseAsHandled (964e668)
• npm was bumped to 12.1.0 with doc refreshes (4eb3908)
• Build/GYP plumbing updated for Temporal/V8 feature flags (9800c29)