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 90.14%. Comparing base (db3a8d8) to head (f30b9ca).
⚠️ Report is 40 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 90.14% 90.14% =======================================
Files 741 741 Lines 242133 242221 +88 Branches 45568 45584 +16 =======================================
+ Hits 218265 218360 +95 
Misses 15371 15371 + Partials 8497 8490 -7 

Files with missing lines	Coverage Δ
lib/net.js	94.43% <96.93%> (+0.06%)	⬆️

... and 27 files with indirect coverage changes

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[Ethan-Arrowood]

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

[jasnell]

Couple of nits but otherwise LGTM

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74931/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74982/

[mcollina]

lgtm

[Ethan-Arrowood]

FYI this is blocked by the broken test-internet workflow affecting a number of PRs right now. Once #64624 lands this will be good to go.

[Ethan-Arrowood]

64624 landed; requested a fresh CI run

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75110/

[guybedford]

Landed in b420cb6.