feat(bluecraft-agentic-docs): add agentic docs skill templates

Add the Bluecraft Agentic Docs skill with guidance for maintaining
root `AGENTS.md` files and `agent-docs/` trees.

Include OpenAI agent metadata plus reference templates and checklists
for root routing, rule docs, inventory docs, and refactor validation.

skills/bluecraft-agentic-docs/references/inventory-doc-template.md

@@ -0,0 +1,54 @@
+# Inventory `agent-docs/` Template
+
+Use this structure for Markdown files inside `agent-docs/` when the document's main job is to track a maintained set of entries: media plans, per-page suggestions, registries, migration queues, or cleanup lists.
+
+## Recommended Shape
+
+```md
+# <Document Title>
+
+<Opening statement: what this inventory tracks, when it should be used or updated, and that it must be followed in scope.>
+
+## Use This For
+
+- <tasks that require reading or updating this inventory>
+
+## Do Not Use This For
+
+- <tasks that belong in a rule doc, public docs, or another inventory>
+
+## Maintenance Rules
+
+- <how to add, update, remove, or rewrite entries>
+
+## Entries
+
+### <Grouping Heading>
+
+#### <Entry Title>
+
+<Recommended fields; keep only the ones that materially help maintainers.>
+
+Source:
+- <path or owning document>
+
+Status:
+- <planned / in progress / complete / remove / optional>
+
+Notes:
+- <what to capture, why it matters, or what to clean up>
+
+## Maintenance Checklist
+
+- <questions for keeping the inventory current and unambiguous>
+```
+
+## Notes
+
+- Prefer an inventory template when the document is mostly a maintained list rather than a rules essay.
+- Start with a small field set. `Source`, `Status`, and `Notes` are common defaults, not mandatory fields.
+- Add, rename, or remove entry fields to match the repository's actual maintenance needs.
+- Keep entry fields stable enough within one document that maintainers can scan and update them consistently.
+- Use grouping headings only when they materially improve navigation.
+- Separate durable maintenance rules from the entries themselves.
+- If the governing policy becomes large, move it to a rule doc and link to it from the inventory.