Specifi nginx via environment variable or skip test

[zealsham]

This pr addresses #1227, it specifies an enironment variable for nginx which will be used during test run. it also removes nginxWithStream package from the dev shell.

i used Claude AI to help me with nix

Pull Request Checklist

Please confirm the following before requesting review:

• I have disclosed my use of
  AI
  in the body of this PR.
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Pull Request Test Coverage Report for Build 20374581801

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 58 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.5%) to 82.905%

---

Files with Coverage Reduction	New Missed Lines	%
ohttp-relay/src/lib.rs	1	79.61%
ohttp-relay/src/bootstrap/ws.rs	57	0.0%

Totals
Change from base Build 20347892595:	-0.5%
Covered Lines:	9670
Relevant Lines:	11664

---

💛 - Coveralls

[nothingmuch]

This looks good, I have only one suggestion to use an error enum { NginxNotAvailable, UnknownError(Box<dyn Error>) } instead of also making the NginxNotAvailable condition into a trait object, since these two branches are handled quite differently

[nothingmuch]

ACK.

since i opened the issue and suggested this solution i think another maintainer should at least concept ACK before merging

[spacebear21]

partial tACK on c8017eb - I tested contrib/test.sh locally without nix and confirmed it skips the problematic tests.

We should be able to also remove the "add nginxWithStream to PATH" step in CI?

[zealsham]

partial tACK on c8017eb - I tested contrib/test.sh locally without nix and confirmed it skips the problematic tests.

We should be able to also remove the "add nginxWithStream to PATH" step in CI?

should that be done in this PR or a different one ?

[spacebear21]

I'm actually not sure if it can be removed, looks like we still need nginxWithStream when setting the new environment variable.