[codex] align global File identity with node:buffer

[andrewtdiz]

Summary

• wires global File to the stdlib File allocator so global File, globalThis.File, and node:buffer File share constructor identity
• routes new globalThis.File(...), rebound constructor calls, and computed dynamic constructor calls through the same File factory
• exposes File-backed Blob handle metadata through generic property dispatch and extends the buffer global-file parity fixture

Validation

• cargo fmt --all -- --check
• git diff --check
• ./scripts/check_file_size.sh
• cargo check -p perry-hir -p perry-codegen -p perry-runtime -p perry-stdlib
• cargo build -p perry -p perry-runtime -p perry-stdlib
• cargo build --release -p perry -p perry-runtime -p perry-stdlib
• PATH=... PERRY_NO_AUTO_OPTIMIZE=1 ./run_parity_tests.sh --suite node-suite --module buffer --filter global-file
• direct Node 26 and Perry debug run of test-parity/node-suite/buffer/blob-file/global-file.ts