The built-in AT Protocol label definitions.

Merge built-in labels with custom labeler-defined labels into a lookup map. Custom labels are keyed by (labelerDid, identifier). Built-in labels use ("", identifier). When looking up, the label source DID is used to prefer custom definitions from the same labeler, falling back to built-in definitions.

Find a built-in label definition by its identifier string.

Find a label definition by identifier and optional labeler DID. First checks for a custom definition from the given labeler, then falls back to the built-in definition.

Interpret a custom label value definition from a labeler into a LabelDefinition. Follows the TypeScript SDK's interpretLabelValueDefinition pattern: maps severity/blurs to context-specific behaviors, sets configurable=true, and adds NoSelf + optional Adult flags.

Interpret multiple custom label value definitions from a labeler. Filters to only valid custom label identifiers (not system labels starting with '!').

Check whether a label identifier matches the custom label value pattern (lowercase letters and hyphens).