mobile: auto-rebuild Dev Tool native client on fingerprint change

[aapeliv]

Adds CI machinery to rebuild the Dev Tool native client automatically when its Expo fingerprint changes — the ~5% case the per-branch OTA pipeline can't serve (a fingerprint mismatch makes the dev client silently ignore branch bundles, so the installed client itself must be rebuilt). Pure JS/TS changes are unaffected; they still load over the air.

How it works — new build:devtool-native job (app/.gitlab-ci.yml) runs on $DEVTOOL_BUILD_BRANCH (set to mobile/v1.1.20 while validating; switch to develop once trusted) and calls app/mobile/scripts/devtool-build.sh per platform:

1. Computes the Expo fingerprint (same expo-updates fingerprint:generate + .fingerprintignore the OTA pipeline uses, so it matches the EAS build).
2. Compares it to the last-built fingerprint at s3://$AWS_PREVIEW_BUCKET/devtool-builds/<platform>.fingerprint. Unchanged → no-op. Changed → build on EAS.
3. iOS → eas build --profile devtool --auto-submit → TestFlight. Android → eas build --profile devtool-apk (new profile: extends devtool, internal distribution, APK); CI downloads the artifact and publishes an immutable couchers-devtool-<sha>.apk + a stable index.html to devtool-builds/android/, served at https://android--devtool-builds.preview.couchershq.org/. Google Play has no TestFlight-equivalent for a dev-client APK, so we self-host it.
4. Writes the fingerprint marker only after a successful build, so a failed build is retried next pipeline.

Also removes the now-dead submit.devtool.android (Play) config and repoints the manual release:android:devtool script at the APK profile.

Requires an EXPO_TOKEN CI variable (Expo robot token, build + submit scope) before the job can run. No Play credentials needed.

Testing

Not yet run end-to-end — needs EXPO_TOKEN in CI. Validated locally:

• bash -n on the script; json_field helper parses both the fingerprint (.hash) and eas build --json ([0].artifacts.applicationArchiveUrl) shapes
• eas.json / package.json valid JSON and prettier-clean; .gitlab-ci.yml parses; devtool-apk profile present, submit.devtool.android removed
• First real run on mobile/v1.1.20 after EXPO_TOKEN is added: confirm a no-op when the fingerprint is unchanged, a build + TestFlight submit (iOS) and APK publish (Android) when it changes, and the stable Android URL serves the APK
• Confirm the android--devtool-builds.preview.couchershq.org host resolves through the existing preview CDN (the tools/lambdas/ aren't in this checkout; relies on the same <a>--<b> → /<b>/<a> mapping OTA uses)

For maintainers

• Maintainers can push commits to my branch
• Maintainers can merge this PR for me

This PR was created with the Couchers PR skill.

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Project	Deployment	Actions	Updated (UTC)
couchers	Ready	Preview	May 24, 2026 8:14pm

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Preview builds

Mobile Dev Tool preview

Scan the QR with your phone camera, or tap Open in Dev Tool on the device, to open this branch in the installed Dev Tool dev client.

ios — Open in Dev Tool

Deep link

couchers-devtool://expo-development-client/?url=https%3A%2F%2F4fda5a60--ota.preview.couchershq.org%2Fios%2Fmanifest

android — Open in Dev Tool

Deep link

couchers-devtool://expo-development-client/?url=https%3A%2F%2F4fda5a60--ota.preview.couchershq.org%2Fandroid%2Fmanifest

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[github-actions]

📝 Release Notes

This PR does not need to be included in release notes.

Reason: This PR adds internal CI automation for rebuilding the mobile Dev Tool native client when needed. It affects developer workflow and preview infrastructure rather than functionality visible to end users, and it does not represent a user-facing feature or broadly important platform change for members using Couchers.

🤖 Bot Debug Information

Model: couchers.openai.gpt-5.4
Decision: exclude
Reasoning: This PR adds internal CI automation for rebuilding the mobile Dev Tool native client when needed. It affects developer workflow and preview infrastructure rather than functionality visible to end users, and it does not represent a user-facing feature or broadly important platform change for members using Couchers.