Restructure Resource Hierarchy documentation to separate IResourceWithParent from lifecycle semantics

[Copilot]

Updates the "Resource Hierarchy and Parent‑Child Relationships" section in docs/specs/appmodel.md to address structural reorganization feedback and improve clarity around IResourceWithParent semantics.

Changes Made

Moved IResourceWithParent out of lifecycle context: The interface discussion is now in the main introduction alongside WithParentRelationship(), clearly establishing that both are purely structural mechanisms:

• IResourceWithParent (static declaration) - establishes structural containment and visual nesting
• WithParentRelationship() (dynamic declaration) - visual nesting only
• IResourceWithParent implies WithParentRelationship()

Removed redundant "Visual Grouping" section: Eliminated the separate section to avoid duplication since visual grouping is now covered in the introduction.

Refocused "Lifecycle Containment" section: Now exclusively discusses lifecycle coordination patterns without any structural relationship concerns:

• Parent drives children (via hooks/orchestration)
• Parent mirrors a child (reflects child's lifecycle/readiness)
• Inherit from children (ad hoc, not standardized)

Added eventing clarification: Added explanation that lifecycle coordination is typically implemented by propagating events to child resources with link to the Well-Known Lifecycle Events section.

Updated Table of Contents: Removed reference to the deleted "Visual Grouping" section.

Impact

This restructuring creates a cleaner separation between structural modeling (IResourceWithParent/WithParentRelationship()) and lifecycle coordination, preventing confusion about when each mechanism should be used and what behaviors they provide. The addition of the eventing link provides clarity on how lifecycle coordination is typically implemented.

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[Copilot]

Pull Request Overview

This PR corrects misleading documentation about resource hierarchy and parent-child relationships in Aspire. The documentation previously incorrectly implied that implementing IResourceWithParent automatically provides lifecycle control, when it actually only establishes structural relationships.

Key Changes

• Clarifies that IResourceWithParent provides structural containment and visual grouping, not automatic lifecycle control
• Separates structural relationships from lifecycle coordination concerns
• Adds explicit examples of lifecycle coordination patterns that must be implemented separately

[Copilot]

This appears to be a heading or section title but lacks proper markdown formatting. Consider adding appropriate markdown heading syntax (e.g., #### Lifecycle coordination (opt-in, resource-specific)) to maintain consistent document structure.

Suggested change

	Lifecycle coordination (opt-in, resource-specific)
	### Lifecycle coordination (opt-in, resource-specific)

[davidfowl]

@copilot move IResourceWithParent out of Lifecycle Containment section. Delete the "Visual Grouping (Without Lifecycle Impact)" section and restate that IResourceWithParent statically declares a parent-child relationship and WithParentRelationship dynamically declares the parent-child relationship (IResourceWithParent implies WithParentRelationship).

Also update the toc where necessary.

[Copilot]

Done. Moved IResourceWithParent out of the "Lifecycle Containment" section to the main introduction, deleted the "Visual Grouping" section, clarified that IResourceWithParent statically declares relationships while WithParentRelationship() dynamically declares them, and updated the TOC. The lifecycle section now focuses purely on coordination patterns. (85ebeef)

[davidfowl]

cc @afscrome @oising