Fix YAML sequence indentation in manifest and mock data files

[nicomiguelino]

Summary

• serde_yaml emits block sequences flush with the parent key (e.g. - item at the same indent level as key:), which does not conform to standard YAML style.
• Adds pretty_yaml as a dependency and introduces a shared format_yaml helper in serde_utils.rs that post-processes serde_yaml::to_string output with Quotes::PreferSingle and indent_block_sequence_in_map: true (the pretty_yaml default).
• Applied at all three YAML write sites: EdgeAppManifest::save_to_file, InstanceManifest::save_to_file, and EdgeAppCommand::generate_mock_data.
• Updates four test assertions in manifest.rs to reflect the corrected indentation.

Before:

---
syntax: manifest_v1
id: test_app
categories:
- Utilities
- Dashboards
entrypoint:
  type: file

After:

---
syntax: manifest_v1
id: test_app
categories:
  - Utilities
  - Dashboards
entrypoint:
  type: file

Test plan

• cargo test — 185 tests pass; one pre-existing failure (test_read_token_correct_token_is_returned) is unrelated to this change and fails on master as well.
• Verified structured help_text (nested mappings with sequences) round-trips correctly through the formatter.
• Manually tested screenly edge-app create and confirmed the generated screenly.yml has properly indented sequence items.
• cargo audit — all findings are pre-existing; pretty_yaml introduces no new vulnerabilities.

[Copilot]

Pull request overview

This PR aims to ensure YAML written by the CLI follows a more conventional indentation style for sequences (e.g., list items indented under their parent key) by formatting serde_yaml::to_string output before writing manifests and mock data.

Changes:

• Added a shared YAML formatter helper (format_yaml) and applied it to all YAML write paths for edge-app manifests and mock data generation.
• Updated manifest serialization tests to match the new sequence indentation.
• Introduced the pretty_yaml dependency (and corresponding lockfile updates) to perform the formatting.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/commands/serde_utils.rs	Adds format_yaml helper based on pretty_yaml for post-processing YAML text.
src/commands/edge_app/server.rs	Formats generated mock-data.yml output before writing to disk.
src/commands/edge_app/manifest.rs	Formats serialized screenly.yml and updates YAML string assertions for indented sequences.
src/commands/edge_app/instance_manifest.rs	Formats serialized instance.yml before writing to disk.
Cargo.toml	Adds pretty_yaml dependency.
Cargo.lock	Locks transitive dependencies introduced by pretty_yaml.

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[salmanfarisvp]

Nix / build (macos-latest) (pull_request)

[nicomiguelino]

@salmanfarisvp, please see #287 for the fix on Nix builds.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.