Align guidelines substrate with the upstream Knowledge rename (Gutenberg #79149 / #77230)

Start by comparing WP_Guidelines_Substrate with upstream Gutenberg proposals #77230 and #79149, then trace how WP_Agent_Memory_Registry and WP_Agent_Context_Section_Registry consume it. First resolve whether to mirror upstream on landing or adopt now with aliases; done requires the chosen rename, compatibility and migration path, updated smoke coverage, and unchanged runtime-contract smokes.

Summary

Agents API ships a WP_Guidelines_Substrate that mirrors the WordPress Guidelines storage primitive: CPT wp_guideline, taxonomy wp_guideline_type, a filterable wp_guideline_types() registry, a scope model (private_user_workspace_memory vs workspace_shared_guidance), the *_workspace_guidelines / *_agent_memory capability namespace (with promote_agent_memory), and a guidelines REST base.

Upstream is consolidating and renaming this primitive from "Guidelines" to "Knowledge", on the rationale that editorial guidelines are just one type of persistent, agent-facing knowledge a site stores — alongside skills, memory, and plans/notes — and they all share the same structural shape (titled, versioned, instructional documents over REST), differing only in lifecycle and multiplicity:

• Proposal: WordPress/gutenberg#77230 — "Evolve CPT to enable support for skills, memory, and plans via taxonomy"
• Reference implementation: WordPress/gutenberg#79149 — "Knowledge: Rename the Guidelines CPT storage primitive to Knowledge"

Our substrate already implements the evolved (typed + private-memory + promote) shape this proposal describes, just under the older guideline names. This issue tracks aligning our names and built-in types with the upstream primitive so consumers target one vocabulary.

Proposed alignment (per gutenberg#79149)

Built-in types, defined by behavior:

• content → instruction (loaded by default when applicable)
• artifact → note (private freeform working text; the save-time fallback term)
• memory stays memory

skill is not a built-in upstream type — it would come through the wp_knowledge_types() filter. Decide whether we ship it as a default here or leave it to consumers.

Considerations

• Timing. gutenberg#79149 is explicitly an illustration of a proposal still gathering feedback (gutenberg#77230). Recommend we track upstream and mirror once it lands rather than rename ahead of it, to avoid churn if the final shape changes — same pattern as #94 (consume Abilities API lifecycle filters once they land). Alternatively, adopt now behind compatibility aliases.
• Backwards compatibility. Consumers already build on the wp_guideline* names, the *_guidelines caps, and the _wp_guideline_* meta. A rename needs a deprecation/aliasing path (old constants/filters delegating to new), plus migration for existing posts/terms/meta.
• Runtime contracts. The consumption side — WP_Agent_Memory_Registry, WP_Agent_Context_Section_Registry, the context injection/conflict-resolution layer — reads through this substrate. The rename is storage-layer + a compatibility shim; the runtime contracts that map instruction / note / memory to agent context should keep working unchanged.

Acceptance

• Decision: mirror-on-land vs adopt-now-with-aliases.
• wp_knowledge CPT + wp_knowledge_type taxonomy + wp_knowledge_types() filter, with the built-in type renames.
• *_knowledge capability namespace and /wp/v2/knowledge REST base.
• Backwards-compatible aliases for the previous names/meta + a migration path.
• Smoke coverage updated for the new names; existing runtime-contract smokes still green.