skills: add SEO/AEO audit and grounded-JSON-LD skills from citeworthyio/seo-agent

Evaluated citeworthyio/seo-agent for reusable process knowledge. Relevant
to this fleet's WordPress content sites (granja travel news, content-agent
pipeline): a crawl-diagnose-approve-recrawl-measure loop for SEO metadata
changes, a three-layer AI-crawler accessibility audit (robots policy, bot
delivery, readable content), and a fail-closed method for generating and
safely injecting Article JSON-LD. Keyword research and citation-probe
pieces of the source repo were skipped as underdeveloped or too
infra-coupled to be reusable here.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

skills/grounded-article-jsonld/SKILL.md

@@ -0,0 +1,61 @@
+---
+name: grounded-article-jsonld
+description: Use when generating, reviewing, storing, or injecting Article JSON-LD from page content. Prevent fabricated machine-readable claims and script-context injection while preserving existing structured data.
+license: MIT
+source: adapted from https://github.com/citeworthyio/seo-agent/blob/b78bb487f2819c3c7cc2ba6f3f5626ea0b841840/README.md#structured-data-json-ld and src/overrides.ts
+---
+
+# Grounded Article JSON-LD
+
+Structured data is a factual publication, not decorative copy. An invented
+author or date becomes a machine-readable claim under the site's name and may
+be consumed without a reader ever seeing and correcting it.
+
+## Generate only from observed page facts
+
+Give the generator only the page content actually fetched: title, description,
+canonical, visible article content, and explicit author/date/image fields. Tell
+it to omit anything it cannot point to in that material. Never infer an author,
+publisher, organization, date, image, rating, price, or other plausible default.
+
+For an article page missing structured data, a minimal correct `Article` object
+with `@context`, `@type`, and a grounded headline is better than a rich-looking
+object containing guesses. Keep automated generation narrow to page-level types
+such as `Article`; organization, product, rating, and similar business claims
+need their own authoritative data source and review process.
+
+## Validate at every boundary
+
+Use the same fail-closed validator for generated drafts, manual proposals, and
+the final publishing write:
+
+1. Parse as JSON.
+2. Accept one object or a non-empty array of objects, never primitives or null.
+3. Require every node to have an `@context` referencing `schema.org` and a
+   non-empty `@type`.
+4. Enforce a bounded canonical serialization (the source implementation uses
+   8,192 characters).
+5. Reject the value rather than storing it if any check fails.
+
+Using one validator matters: otherwise a draft can pass review and fail at
+publish time, or a manual path can bypass the protections applied to AI output.
+
+## Canonicalize for safe script embedding
+
+Store JSON text without a `<script>` wrapper. After parsing, serialize it again
+and replace literal `<` and `>` in the serialized bytes with JSON escapes
+`\u003c` and `\u003e`. A JSON parser reconstructs the original characters, but
+the stored bytes cannot close an enclosing script element or open an HTML
+comment—even when the input expressed `<` through a JSON escape.
+
+Do not use HTML entities such as `&lt;` inside JSON: they change the data rather
+than safely encoding JSON for a script context. At injection time, reject any
+stored value that unexpectedly contains a literal `<`; it did not pass the
+canonical write path.
+
+Add the validated block alongside existing JSON-LD instead of replacing it.
+Multiple blocks are valid, while overwriting an origin block can silently erase
+publisher-authored facts. Verify the public response contains a parseable block
+of the intended type; presence proves less than byte-for-byte comparison, so do
+not overstate what that check establishes.
+