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-package.md

@@ -0,0 +1,39 @@
+# Core-package generator
+
+`pnpm turbo gen core-package` scaffolds an optional core package back into a slimmed template. Each name maps to a verbatim copy of the package as it shipped at the time the generator was added.
+
+## Usage
+
+```bash
+pnpm turbo gen core-package
+# → Which optional core package? (use arrow keys)
+#   ❯ realtime
+#     events
+#     trpc
+#     ui
+```
+
+The generator emits the package files, updates consuming-app config (e.g. `apps/web-next/next.config.mjs` `transpilePackages`), patches `packages/core-eslint/base.js` to re-add any package-specific lint rules, then prints the manual app/server wiring needed to bring the package fully online.
+
+## Available templates
+
+| Name       | Description                                              |
+| ---------- | -------------------------------------------------------- |
+| `realtime` | Socket.IO realtime layer (ADR-016)                       |
+| `events`   | Cross-feature event bus + Payload jobs adapter (ADR-015) |
+| `trpc`     | tRPC server setup                                        |
+| `ui`       | Design-system package                                    |
+| `audit`    | DPA-compliant audit logging (ADR-018)                    |
+
+## Verifying an existing project
+
+If your project already has a core-\* package and you want to verify the generator's template hasn't drifted from the shipped source, use the byte-identical reconstruction snapshot:
+
+```bash
+git stash -u
+pnpm turbo gen core-package <name>
+git diff packages/core-<name>/
+# Expect: zero diff (modulo .hbs strip + trailing-newline normalization)
+```
+
+Snapshots live at `turbo/generators/__snapshots__/core-package/<name>.snapshot.json`.