[WIP] Add AppKit template to bundle init

[lennartkats-db]

Changes

• Add app-appkit to databricks bundle init, reusing the initializer behind databricks apps init.
• Support non-interactive initialization with --config-file and project_name, and update help and changelog.

Why

AppKit apps use bundles for deployment. Exposing the template through bundle init lets users find and scaffold them alongside the other bundle templates.

Tests

• ./task checks and GOTOOLCHAIN=go1.26.9 ./task lint-go passed.
• Focused Go and acceptance tests passed, including non-interactive initialization, validation, fake-server deploy, and destroy.
• 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.
• Full local ./task fmt could not fetch Ruff (PyPI DNS). ./task test had failures in JSON error expectations and local Node/shell setup; the focused AppKit cases passed.

Authored with Codex.

[github-actions]

Thanks for the contribution! This pull request was opened from a fork.

If you're a member of the Databricks organization, please request access to the cli-contrib team and open your pull request from a branch in this repository instead of a fork — fork PRs don't run integration tests automatically and have reduced CI access.

If you're an external contributor, no action is needed; a maintainer will review your pull request.

[github-actions]

An authorized user can trigger integration tests manually by following the instructions below:

Trigger:
go/deco-tests-run/cli

Inputs:

• PR number: 7004
• Commit SHA: 902c15161b5aa49cd5e87b4c5d56bfa8a7a8672a

Checks will be approved automatically on success.