refactor(ci): consolidate the CI-env scrubber into a shared testing module

[jd]

with_ci_env (clear every CI-provider env var before applying
test overrides) lived in two copies — one inside the tests
sub-module of detector.rs, one inside scopes_send.rs (which
also had a with_ci_env_async counterpart). Both spelled the same
10-var list inline; both were drifting candidates.

Extract to a new crate::testing (#[cfg(test)] mod testing) with
the env-var list named as a const, sync + async variants behind one
helper that builds the override list. Each test module now does a
plain use crate::testing::with_ci_env;.

Net -71 / +51. No behavior change; the existing 49 mergify-ci
tests still pass.

Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com

Depends-On: #1441

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	fix(cli): accept --debug on the Rust binary and actually toggle it in Python	#1464
2	refactor(rust): share test scaffolding via mergify-test-support crate	#1439
3	refactor(core): introduce CommandContext for the queue+freeze prelude	#1441
4	refactor(ci): consolidate the CI-env scrubber into a shared testing module	#1442	👈
5	refactor: drop stale Phase X.Y doc markers and one inline color branch	#1443
6	refactor(tui): share StyledGlyph across queue show/status renderers	#1444
7	refactor(queue): drop indexmap, group_by_scope returns a Vec<(K, V)>	#1445
8	refactor(ci): swap uuid for getrandom in the GHA heredoc delimiter	#1446
9	refactor(config): standardize the workspace on serde_yaml_ng for YAML parsing	#1447
10	test(ci): add live smoke test for ci scopes select-all path	#1460
11	feat(rust): port ci scopes to native Rust	#1461
12	feat(ci): parse JUnit XML reports in native Rust	#1465
13	feat(ci): encode JUnit cases as OTLP and upload to Mergify CI Insights	#1466
14	feat(ci): promote ci junit-process from shim to native Rust	#1467
15	feat(ci): promote ci junit-upload from shim to native as a deprecated alias	#1468
16	fix(ci): prefer GitHub Actions PR-event head SHA over GITHUB_SHA	#1469

[mergify]

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[jd]

Revision history

#	Type	Changes	Reason	Date
1	initial	9484593		2026-05-19 13:04 UTC
2	rebase	9484593 → 3e6ba1c (rebase only)		2026-05-19 13:04 UTC
3	rebase	3e6ba1c → 6d57a9c (rebase only)		2026-05-19 14:15 UTC
4	rebase	6d57a9c → a946696 (rebase only)		2026-05-20 08:42 UTC
5	rebase	a946696 → fcfd504 (rebase only)		2026-05-20 09:05 UTC
6	rebase	fcfd504 → 2b55249 (rebase only)		2026-05-21 07:25 UTC
7	rebase	2b55249 → b12bb5c (rebase only)		2026-05-21 07:56 UTC
8	rebase	b12bb5c → 8b64b4d (rebase only)		2026-05-21 12:39 UTC
9	content	8b64b4d → ab88212		2026-05-22 07:10 UTC
10	rebase	ab88212 → 3f12d27 (rebase only)		2026-05-22 14:40 UTC
11	rebase	3f12d27 → 3d06f0f (rebase only)		2026-05-27 07:53 UTC
12	rebase	3d06f0f → d7c68e9 (rebase only)		2026-05-27 08:27 UTC
13	content	d7c68e9 → 5b8ad61 (raw)	Scrub GITHUB_OUTPUT in the canonical CI_ENV_VARS list — moved here from the Phase B expansion so PRs lower in the stack (#1465 parse JUnit XML) inherit the fix and stop hitting GHA's 'Matching delimi…	2026-05-27 10:04 UTC