fix(env-http-proxy-agent): match bare IPv6 addresses in no_proxy

[marko1olo]

This relates to...

Issue #5616 — EnvHttpProxyAgent silently ignores a bare (unbracketed) IPv6 address in NO_PROXY.

Rationale

Two bugs cooperate to produce the silent mismatch:

1. #parseNoProxy misidentifies bare IPv6 as host+port.
The regex /^(.+):(\d+)$/ matched on ::1 and split it into host :: with port 1.
Entries like ::1 were stored with the wrong key and never matched.

2. #getProxyAgentForUrl kept URL brackets, #parseNoProxy did not.
URL.host returns [::1]; the code stripped :PORT but left the surrounding brackets,
so [::1] ≠ ::1 even if the hostname stored in noProxyEntries happened to be correct.

Changes

lib/dispatcher/env-http-proxy-agent.js

• #parseNoProxy: handle bracketed-IPv6-with-port ([::1]:443) with an explicit regex first;
  for everything else, count colons — more than one colon unambiguously means a bare IPv6
  literal (store as-is, port 0), exactly one colon means hostname:port (split normally).

• #getProxyAgentForUrl: after stripping the port suffix, also strip surrounding brackets
  from the hostname so the result matches the unbracketed form stored by #parseNoProxy.

test/env-http-proxy-agent.js

New test: bare IPv6 addresses in no_proxy are matched (issue #5616) — covers ::1, [::2]:80,
and ::3 in the same NO_PROXY string. All 36 env-http-proxy-agent tests pass.

Features

• Implemented a new feature

Bug Fixes

• Fixed a bug

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.51%. Comparing base (c76fe46) to head (f67b4a1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5623      +/-   ##
==========================================
+ Coverage   93.49%   93.51%   +0.01%     
==========================================
  Files         110      110              
  Lines       38429    38451      +22     
==========================================
+ Hits        35931    35957      +26     
+ Misses       2498     2494       -4     

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[mcollina]

lint

[marko1olo]

Fixed formatting (removed redundant empty lines) in f67b4a15. Linter is clean.

[mcollina]

lgtm