Replace name-based model specifiers with IDs in modeling commands

[angeloashmore]

Modeling commands currently accept names/labels to identify slices and content types. These should be replaced with IDs for consistency and reliability.

Affected flags/arguments

Slice specifiers (currently accept slice name):

• slice view, slice remove, slice connect, slice disconnect — positional argument
• --to-slice, --from-slice — used across field commands
• slice add-variation --to, slice remove-variation --from

Content type specifiers (currently accept type label):

• type view, type remove — positional argument
• --to-type, --from-type — used across field commands
• slice connect --to, slice disconnect --from

Notes

• Slice lookups use s.name, type lookups use ct.label — neither uses the model ID
• slice create and type create accept a name and derive the ID via snakeCase(name) — these may be fine as-is since they're creating new models
• Core resolution logic lives in src/models.ts (resolveModel, resolveFieldContainer)