Lands the v1.0 purpose registry (WS-2 of the consolidation sprint) as a
first-class concept: a `PurposeDefinition` value object, a
`PurposeRegistry` service keyed by slug, and a declarative
`config/form_builder/purposes.php` registry with exactly the seven
purposes from ARCH-CONSOLIDATION §6.4.
Also rebuilds the morph-map in `AppServiceProvider::boot` into three
labelled blocks: (1) domain subject types derived from
`PurposeRegistry::allSubjectTypes()`, (2) non-purpose domain types
hardcoded with comments (form_schemas owner_types, activity-log
subjects), (3) framework types (spatie/activitylog; Sanctum stays
absent per addendum Q4).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>