epic(extensions): ship the peer-extension platform for v0.5.x

[DecisionNerd]

Objective

Ship and prove a reusable peer-extension platform over the published gf-api while keeping GraphForge Core extension-agnostic.

Workstreams

• epic: datasets as the first peer extension (gf-datasets) — v0.5.x #20 — dataset infrastructure, reference content, packaging, and author template.

• feat(extension): ship local-first genealogy interoperability for GEDCOM 7 and GEDCOM X JSON #21 — local-first genealogy interoperability as a reference domain extension.

• extension: publish a queued GraphForge authority artifact #215 — optional queued-authority MCP/HTTP transport as a peer extension.

• research(extensions): investigate browser client and XYG integration with native GraphForge #1200 — investigate browser-client versus XYG-adapter ownership for native GraphForge results; closes on an evidence-backed recommendation, not package implementation.

• feat(extensions): evaluate and deliver optional decision-model adapters #1574 — optional decision-model evaluation and adapters over M12 public contracts; post-release, with no Core vendor dependency.

Acceptance criteria

1. Every extension depends only on published public GraphForge APIs; Core never depends on an extension and remains buildable when extensions are deleted.
2. Boundary and deletion checks enforce the dependency direction.
3. Applicable Rust, Python, and Node packages pass fresh-build or clean-install acceptance.
4. Documentation provides a working third-party extension path.
5. Each native workstream and its children satisfy their own outcome-based acceptance criteria.

Non-goals

• Adding MCP, HTTP, authentication, authorization, or server lifecycle to Core.
• Distributed consensus, network-mounted project directories, or multiple storage authorities.
• Blocking v0.5.0 publication on post-release extension work.
• Building an extension marketplace or UI.

Relationships

• Milestone tracker for M15: Peer Extensions (after v0.6.0).
• The workstream issues are native sub-issues; detailed implementation remains in those workstreams. research(extensions): investigate browser client and XYG integration with native GraphForge #1200 adds investigation only and does not block existing implementation or v0.6.0 publication.