refactor(docs): consolidate scaffolding/ into guides/

The docs/scaffolding/ directory held two how-to guides (core-package
+ core-ui-component generator references). Both are operationally
identical in shape to docs/guides/scaffolding-a-feature.md — they
just live in a separate top-level docs directory. Consolidating
removes one directory + makes the three scaffolding guides
discoverable as siblings.

Moves (via git mv to preserve history):
  docs/scaffolding/core-package-generator.md
    -> docs/guides/scaffolding-core-package.md
  docs/scaffolding/core-ui-component-generator.md
    -> docs/guides/scaffolding-core-ui-component.md

Empty docs/scaffolding/ directory removed.

AGENTS.md (only consumer of the old paths) updated to point at the
new locations.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/guides/scaffolding-core-ui-component.md

@@ -18,12 +18,12 @@ pnpm turbo gen core-ui-component
 
 The generator emits 4 files into `packages/core-ui/src/<tier>s/<kebab-name>/`:
 
-| File | Purpose |
-|---|---|
-| `<kebab-name>.tsx` | Component implementation (forwardRef + cn + className passthrough) |
-| `<kebab-name>.stories.tsx` | Storybook stories (Meta + StoryObj + one Default story; tier-prefixed title) |
-| `<kebab-name>.test.tsx` | Vitest + Testing Library smoke tests (renders, className passthrough, ref forwarding) |
-| `index.ts` | Barrel that re-exports the component + Props type |
+| File                       | Purpose                                                                               |
+| -------------------------- | ------------------------------------------------------------------------------------- |
+| `<kebab-name>.tsx`         | Component implementation (forwardRef + cn + className passthrough)                    |
+| `<kebab-name>.stories.tsx` | Storybook stories (Meta + StoryObj + one Default story; tier-prefixed title)          |
+| `<kebab-name>.test.tsx`    | Vitest + Testing Library smoke tests (renders, className passthrough, ref forwarding) |
+| `index.ts`                 | Barrel that re-exports the component + Props type                                     |
 
 The new export is also spliced into `packages/core-ui/src/<tier>s/index.ts` immediately after the `// <gen:<tier>s>` anchor, so the component is reachable from the tier barrel (and transitively from the root `@repo/core-ui` export) without any manual wiring.