Move entity rehydration to domain layer, fix tempHp gap

Rehydration functions (reconstructing typed domain objects from untyped
JSON) lived in persistence adapters, duplicating domain validation.
Adding a field required updating both the domain type and a separate
adapter function — the adapter was missed for `level`, silently dropping
it on reload. Now adding a field only requires updating the domain type
and its co-located rehydration function.

- Add `rehydratePlayerCharacter` and `rehydrateCombatant` to domain
- Persistence adapters delegate to domain instead of reimplementing
- Add `tempHp` validation (was silently dropped during rehydration)
- Tighten initiative validation to integer-only
- Exhaustive domain tests (53 cases); adapter tests slimmed to round-trip
- Remove stale `jsinspect-plus` Knip ignoreDependencies entry

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

knip.json

@@ -1,6 +1,5 @@
 {
 	"$schema": "https://unpkg.com/knip@5/schema.json",
-	"ignoreDependencies": ["jsinspect-plus"],
 	"workspaces": {
 		".": {
 			"entry": ["scripts/*.mjs"]