feat: replace name-based model specifiers with IDs

[angeloashmore]

Resolves: #105

Description

Replace name-based model specifiers with IDs in all modeling commands. Slice commands now resolve by id instead of name, content type commands resolve by id instead of label, and variation commands resolve by id instead of name.

Checklist

• A comprehensive Linear ticket, providing sufficient context and details to facilitate the review of the PR, is linked to the PR.
• If my changes require tests, I added them.
• If my changes affect backward compatibility, it has been discussed.
• If my changes require an update to the CONTRIBUTING.md guide, I updated it.

Preview

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Note

Medium Risk
This changes CLI arguments for many modeling commands from name/label-based lookups to ID-based lookups, which is a backward-incompatible behavior change and may break existing scripts. Logic changes are straightforward but touch multiple commands and shared model resolution paths.

Overview
Model targeting is now ID-based across the CLI. Slice commands (add-variation, connect/disconnect, edit, remove, view, and variation edit/remove) now resolve the target slice/variation via id rather than name.

Content type commands follow the same shift. Type commands (edit, remove, view, tab add/edit/remove) now resolve content types via id rather than label, and shared field-model resolution in src/models.ts updates --to-*/--from-* options and lookups accordingly.

Tests and --help expectations are updated throughout to pass IDs and assert the new output/messages.

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