net: support AF_UNIX paths in net.BoundSocket

[guybedford]

Extends net.BoundSocket (#63951) with a path option so it can immediately bind a named unix-domain socket (or Windows pipe) synchronously, not just TCP. This gives a public synchronous UDS bind through the same role-neutral handle, instead of reaching into process.binding('pipe_wrap'), just as it replaces the need for tcp_wrap and udp_wrap similarly.

path is mutually exclusive with host/port/ipv6Only/reusePort, and binds in the constructor so conflicts throw there like TCP does. A leading '\0' uses the Linux abstract namespace; an abstract path elsewhere throws ERR_INVALID_ARG_VALUE.

• address() returns the path string for a pipe (as Server.address() does), the address object for TCP.
• New isPipe getter to tell the two apart.
• server.listen(bound) and new net.Socket({ handle: bound }).connect() pick pipe vs TCP from the adopted handle's type.
• A bound client pipe reports its source path as localAddress.

Note two error codes match libuv rather than intuition: missing parent dir is EACCES (libuv maps ENOENT), over-long path is EINVAL (UV_PIPE_NO_TRUNCATE).

Tests cover sync bind + address(), duplicate-bind EADDRINUSE, the listen/connect round-trip, bound-client localAddress, the abstract namespace, and the error paths.

[nodejs-github-bot]

Review requested:

• @nodejs/net

[codecov]

Codecov Report

❌ Patch coverage is 96.93878% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.25%. Comparing base (8fec65d) to head (9571737).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/net.js	96.93%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64399      +/-   ##
==========================================
- Coverage   90.25%   90.25%   -0.01%     
==========================================
  Files         741      741              
  Lines      241207   241427     +220     
  Branches    45430    45495      +65     
==========================================
+ Hits       217698   217892     +194     
- Misses      15084    15090       +6     
- Partials     8425     8445      +20     

Files with missing lines	Coverage Δ
lib/net.js	94.66% <96.93%> (+0.06%)	⬆️

... and 31 files with indirect coverage changes

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[Ethan-Arrowood]

LGTM with just some doc changes and one question about the implementation.

[Ethan-Arrowood]

What happens here if this._handle is null from the if (this.destroyed) { line just before?

[guybedford]

Good catch! Yeah it would wrongly attempt a TCP connect - fixed to fall back to the path option if the handle is already gone.