[Docs] Explain CLI and AI scaffolding through one feature

[divyarajmasani]

Parent epic: #768 — Documentation epic

Base branch: theme-elementary-v2. Cover its functionality and subsequent changes based on it. Verify against the latest relevant v2 implementation and record the tested commit in the documentation PR.

Problem and scope

Developers need to know when to use CLI or AI, what each produces, and how generated code fits this skeleton. Create docs/scaffolding.md using one representative feature in both workflows.

Proposed structure

1. Choose a workflow: a compact comparison of generated stubs, implementation, wiring, tests, and developer responsibilities.
2. Before generating: correct directory, initialized identity, dependencies, and relevant theme conventions.
3. CLI example: discover/preview, generate, inspect files, wire the feature, and identify remaining implementation and checks.
4. AI example: the equivalent brief, expected confirmations, generated result, and remaining developer actions.
5. Verify the result: expected paths, registration, visible behavior, and a focused check.
6. Find other scaffolds: direct links to the wp-tooling catalogue and detailed options.
7. Troubleshooting: wrong output directory, missing inputs, duplicate registration, and missing build output.

Boundaries

• Use the same small feature in both routes; do not require a complete tutorial for every scaffold kind.
• Explain skeleton-specific namespace, source/test paths, text domain, build location, and wiring. Link detailed engine reference upstream.
• Where engine defaults differ from this theme, show the required arguments next to the example.
• Briefly identify companion-plugin placement for persistent functionality such as CPTs/taxonomies.
• Link to DEVELOPMENT.md for manual extension and wp-framework for detailed class behavior.
• A theme-aware wrapper is a separate implementation proposal, not a command to document before it exists.

Acceptance criteria

• One feature illustrates both routes and their different responsibilities.
• Both routes use the same intended project structure.
• Developers can locate generated files, activate the feature, and identify unfinished work.
• Raw commands include required theme conventions and are tested.
• Other scaffold kinds and exhaustive options are linked to wp-tooling.
• The guide does not duplicate the manual extension tutorial or AI skill internals.