Node gains Buffer.isLatin1 and hot-path wins

buffer: add isLatin1

Adds buffer.isLatin1() for fast validation of strings that can be losslessly encoded as Node.js 'latin1'/WebIDL ByteString. This gives users a direct API for a common check and comes with docs, benchmarks, and tests. (8f43e88)

module: remove per-require cache key allocation

require() no longer builds a concatenated cache-key string on every load; the relative resolve cache is now organized by parent directory first, with per-directory request lookups. That reduces allocation pressure on the hot path and improves both throughput and memory use. (471fe81)

buffer: fix negative index results for large buffers

Buffer#indexOf() and lastIndexOf() now return correct positions for matches beyond 2 GiB instead of truncating large offsets. The fix updates the C++ index return types and adds coverage for number, Buffer, and string searches on very large buffers. (e6d4720)

http2: emit close for aborted HEAD compat responses

HTTP/2 compat responses for HEAD requests now distinguish between a headers-only response and a response that was aborted before headers were sent. That restores expected close/finish behavior so aborts are observable and HEAD responses still behave like HTTP/1 compat. (191a3b2)

Other misc changes

• Stream/webstreams hot-path optimization and related benchmark scaffolding (cff7b12)
• Deflake fast FFI buffer tests (58821ee)
• Pipe/socket test path portability fix on macOS (ae9c25a)
• Several flaky-status cleanup commits across loader, exit timeout, CPU profiler, SEA, and renamed tests (c570b67, c12d483, 1a15692, cbf3566, e0a3c37)