Add AppKit template to bundle init

[lennartkats-db]

Changes

• Add app-appkit to databricks bundle init by calling the existing databricks apps init initializer. The production template remains in databricks/appkit.
• Support non-interactive initialization with --config-file and project_name, and update help and changelog.

Why

AppKit apps use bundles for deployment. Listing AppKit in bundle init lets users discover and scaffold one alongside the other bundle templates.

Tests

• Existing apps init acceptance tests cover AppKit initializer options. The new bundle init app-appkit acceptance test covers non-interactive config-file handling and validation, deploy, and destroy of the generated bundle using a small local test fixture.
• ./task checks and GOTOOLCHAIN=go1.26.9 ./task lint-go passed. PR CI passed across Linux, macOS, and Windows, including integration tests.
• An AppKit 0.76.1 scaffold initialized with closed stdin passed strict validation. On dogfood, the app reached ACTIVE and its deployment reached SUCCEEDED; the temporary app was deleted.

Authored with Codex.

[eng-dev-ecosystem-bot]

Integration test report

Commit: a8e2d22

Run: 39272567749

	Env	🔄​flaky	✅​pass	🙈​skip	Time
🔄​	aws linux-2core-8gb	2	274	18	5:53
✅​	aws-windows-latest-4core-16gb		278	16	3:52
✅​	azure linux-2core-8gb		275	18	5:36
✅​	azure-windows-latest-4core-16gb		277	16	5:00
✅​	gcp linux-2core-8gb		276	18	5:40
✅​	gcp-windows-latest-4core-16gb		278	16	5:44

	Test Name	aws linux-2core-8gb
🔄​	TestFsCpFileToFileWithOverwriteFlag/uc-volumes_to_dbfs	🔄​f
🔄​	TestFsCpFileToFileWithOverwriteFlag/uc-volumes_to_local	🔄​f

Top 6 slowest tests (at least 2 minutes):

duration	env	testname
5:36	gcp-windows-latest-4core-16gb	TestAccept
4:54	azure-windows-latest-4core-16gb	TestAccept
3:55	azure linux-2core-8gb	TestAccept
3:52	aws linux-2core-8gb	TestAccept
3:50	gcp linux-2core-8gb	TestAccept
3:45	aws-windows-latest-4core-16gb	TestAccept

[MarioCadenas]

The thing I don't like about this is that we are now duplicating the appkit template into 2 places and we don't have a source of truth anymore, is there anything we can do to change this? can we maybe make databricks bundle init when choosing appkit an alias of databricks apps init or something like that? just my opinion 😄

[lennartkats-db]

@MarioCadenas

The thing I don't like about this is that we are now duplicating the appkit template into 2 places and we don't have a source of truth anymore, is there anything we can do to change this? can we maybe make databricks bundle init when choosing appkit an alias of databricks apps init or something like that? just my opinion 😄

That’s the intended behavior here: bundle init app-appkit calls the existing apps init initializer, so databricks/appkit remains the production source of truth. The template files in acceptance/ are a local test fixture. I’ll make that distinction clearer in the PR description.