fix(filament): guard ProductForm status callouts against a null record - #2584

Problem

Mounting Schemas\Product\ProductForm without a record — as any resource Create page does — throws a TypeError on every load, before the form can render.

The status-callout closures in getStatusShouts() type-hint a non-nullable Model $record, and getVariantAttributeDataComponent() a non-nullable Product $record. Filament injects a null record on create, so evaluation fails at the closure boundary — the existing null-safe isDraft() / isPublished() helpers never get a chance to run.

TypeError: {closure}(): Argument #1 ($record) must be of type Illuminate\Database\Eloquent\Model, null given
  at packages/filament/src/Schemas/Product/ProductForm.php:60

Reproduced on 2.x. A downstream panel that wires ProductForm::configure() onto a Create page hits this immediately (the bundled lunarphp/admin ProductResource ships no standard Create page, which is why it hasn't surfaced there).

Fix

• Widen the six status-callout closures to ?Model $record and the variant closure to ?Product $record.
• Only the two closures that dereference the record directly — $record->channels() and $record->hasVariants — gain an explicit $record === null || guard. The rest already short-circuit through the nullable isPublished()/isDraft() helpers, so no redundant null check is added.
• hasEnabledCustomerGroup() and isDefaultGroupVisibleToGuests() now accept ?Model and guard internally, matching the existing isPublished()/isDraft()/isArchived() helpers.

Behaviour is unchanged once a record exists. No public method signatures change (widening a parameter type is contravariant / LSP-safe); README is untouched, CHANGELOG gets a bugfix entry.

Tests

New bridge-suite test tests/filament/Unit/Schemas/Product/ProductFormTest.php:

• Evaluates every status component inside a real schema container with a null record — fails with the TypeError before this change, passes after.
• Guards that the draft callout still tracks a persisted product's status (visible for a draft, hidden for a published product).

vendor/bin/pest --testsuite=filament   # 47 passed
vendor/bin/phpstan analyse -c phpstan.neon.dist   # no errors (level 0)
vendor/bin/pint --dirty                # pass