feat: add resource metadata to Ash.NotLoaded struct

[nallwhy]

Contributor checklist

Leave anything that you believe does not apply unchecked.

• I accept the AI Policy, or AI was not used in the creation of this PR.
• Bug fixes include regression tests
• Chores
• Documentation changes
• Features include unit/acceptance tests
• Refactoring
• Update dependencies

Summary

• Add a resource field to Ash.NotLoaded struct so consumers can identify which resource a not-loaded field belongs to
• Populate resource in all places where Ash.NotLoaded is constructed: struct defaults (relationships, aggregates, calculations) and action helpers (attributes)
• Show resource in standalone Ash.NotLoaded inspect output, but hide it inside resource record inspect to keep output clean

Closes #885

[Copilot]

Pull request overview

Adds resource metadata to Ash.NotLoaded so callers can identify which resource a not-loaded field belongs to, while keeping resource record inspect/1 output uncluttered.

Changes:

• Added :resource field to %Ash.NotLoaded{} and updated its Inspect implementation to optionally display it.
• Populated resource when constructing %Ash.NotLoaded{} in resource struct defaults (relationships/aggregates/calculations) and attribute select masks.
• Updated resource record inspection to mark nested inspection as in_resource? so Ash.NotLoaded can hide resource in that context, and added tests covering defaults + inspect behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
lib/ash/not_loaded.ex	Adds resource to the struct/typespec and conditionally renders it in Inspect.
lib/ash/resource/schema.ex	Ensures struct default %Ash.NotLoaded{} values include resource: __MODULE__ for relationships/aggregates/calculations.
lib/ash/actions/helpers.ex	Includes resource in %Ash.NotLoaded{} created for unselected attributes in select masks.
lib/ash/resource.ex	Sets Inspect custom option in_resource?: true when inspecting resource fields so nested NotLoaded hides resource.
test/not_loaded_test.exs	Adds unit tests for the new resource field and inspect behavior (standalone vs inside resource).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[zachdaniel]

🚀 Thank you for your contribution! 🚀