build: Disable Android debug variants outside the sample app

[runningcode]

📜 Description

Unit tests already run against the release variant (testBuildType = "release"), and CI already disabled the Android debug variant. This makes the same thing happen locally:

• Config.Android.shouldSkipDebugVariant now skips the debug variant everywhere (not just in CI), so local builds of the libraries and integration-test apps match CI and no longer configure/build the unused debug variant.
• The sample app (sentry-samples-android) keeps both debug and release variants locally and in CI, so manual runs and btrace profiling (installDebug) still work.
• Updated the contributor docs (AGENTS.md, .cursor/rules/coding.mdc) and the test skill to reference testReleaseUnitTest instead of testDebugUnitTest.
• Refreshed the now-stale "CI disables the debug variant" comments in the Android module build files and simplified the snapshot-outputs task matcher in sentry-android-core to the release task.

💡 Motivation and Context

All unit tests use the release variant, so the debug variant only added build/configuration overhead locally, and the docs pointed contributors (and agents) at a testDebugUnitTest task that no longer runs.

💚 How did you test it?

• ./gradlew :sentry-android-core:tasks --all — only testReleaseUnitTest is present; no assembleDebug/testDebugUnitTest.
• ./gradlew :sentry-samples:sentry-samples-android:tasks --all — both installDebug/assembleDebug and their release counterparts remain.
• ./gradlew spotlessApply apiDump — passes with no API changes.

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

#skip-changelog

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.50.0 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	362.69 ms	437.89 ms	75.20 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
eb95ded	317.51 ms	369.08 ms	51.57 ms
2124a46	319.19 ms	415.04 ms	95.85 ms
c3ee041	310.64 ms	361.90 ms	51.26 ms
dcc6bbf	382.58 ms	462.13 ms	79.54 ms
7a19fee	315.46 ms	368.62 ms	53.16 ms
9054d65	330.94 ms	403.24 ms	72.30 ms
d500866	326.13 ms	378.70 ms	52.58 ms
ad8da22	365.86 ms	427.00 ms	61.14 ms
ed33deb	337.52 ms	484.06 ms	146.54 ms
d15471f	310.26 ms	377.04 ms	66.78 ms

App size

Revision	Plain	With Sentry	Diff
eb95ded	0 B	0 B	0 B
2124a46	1.58 MiB	2.12 MiB	551.51 KiB
c3ee041	0 B	0 B	0 B
dcc6bbf	1.58 MiB	2.12 MiB	553.10 KiB
7a19fee	0 B	0 B	0 B
9054d65	1.58 MiB	2.29 MiB	723.38 KiB
d500866	0 B	0 B	0 B
ad8da22	1.58 MiB	2.29 MiB	719.83 KiB
ed33deb	1.58 MiB	2.13 MiB	559.52 KiB
d15471f	1.58 MiB	2.13 MiB	559.54 KiB