ZEA-4455: zbpack.json schema

[pan93412]

Description (required)

• refactor(planner/rust): Use the standard app_dir
• feat: Add zbpack JSON schema

Related issues & labels (optional)

• Closes ZEA-4455
• Suggested label: enhancement

[Copilot]

Pull Request Overview

This pull request implements a schema update for zbpack JSON and refactors the Rust planner to use a standardized application directory key.

• Refactors configuration key for application directory (from "rust.app_dir" to "app_dir").
• Adjusts tests to verify both legacy and new configuration key behavior.

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
internal/rust/rust_test.go	Updates tests to use the legacy key and verifies new behavior.
internal/rust/plan.go	Refactors configuration key definitions and error handling in getAppDir.

Files not reviewed (1)

• schema/zbpack.json: Language not supported

Comments suppressed due to low confidence (1)

internal/rust/plan.go:30

• [nitpick] The new key 'app_dir' for ConfigRustAppDir may cause confusion with the legacy key 'rust.app_dir'. Ensure that documentation and configuration migration paths clearly explain this change.

const ConfigRustAppDir = "app_dir"