docs(HUB-WP-0004): propose runtime consolidation and extension contract

Parent prj-state-hub-retirement SHR-WP-0001 stream S2.

workplans/HUB-WP-0004-runtime-and-extension-contract.md

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+---
+id: HUB-WP-0004
+type: workplan
+title: "Runtime consolidation and extension contract"
+domain: infotech
+repo: hub-core
+status: proposed
+owner: codex
+topic_slug: infotech
+created: "2026-08-09"
+updated: "2026-08-09"
+parent_project: prj-state-hub-retirement
+parent_workplan: SHR-WP-0001
+related:
+  - HUB-WP-0003
+  - CORE-WP-0010
+  - SHR-ARCH-HUB-0001
+  - SHR-ARCH-IA-0001
+---
+
+# Runtime consolidation and extension contract
+
+## Goal
+
+Evolve hub-core from library-only into the **surviving HelixForge hub framework
+and runtime**, shipping `helixforge.hub-extension` Tier 1 artefacts and a clear
+path to absorb core-hub production traffic.
+
+Coordinated by `prj-state-hub-retirement` (SHR-WP-0001). Architecture:
+`architecture/hub-extension-architecture_v0.1.md`.
+
+## Adopt project architecture freeze
+
+```task
+id: HUB-WP-0004-T01
+status: todo
+priority: high
+```
+
+Review and accept SHR-ARCH-IA-0001 and SHR-ARCH-HUB-0001 as the vocabulary for
+ports, kinds, and extension packages. Record gaps as tasks, not silent drift.
+
+## Ship extension contract Tier 1 artefacts
+
+```task
+id: HUB-WP-0004-T02
+status: todo
+priority: high
+```
+
+Publish versioned hub descriptor schema, manifest schema, event-type catalog
+schema, and port OpenAPI fragments for `helixforge.hub-extension` 0.1+, plus a
+sample hub fixture. Align with `hub-extension-contract_v0.1.yaml`.
+
+## Define runtime packaging decision
+
+```task
+id: HUB-WP-0004-T03
+status: todo
+priority: high
+```
+
+Record whether hub-core ships a primary runtime image (recommended) with the
+library remaining importable, vs library + permanent thin host. Decision before
+absorbing core-hub routes.
+
+## Implement core ports (minimal vertical)
+
+```task
+id: HUB-WP-0004-T04
+status: todo
+priority: high
+```
+
+Expose minimal working surfaces for `port.registry`, `port.messaging`,
+`port.events.progress`, `port.events.interaction`, and `port.projection.query`
+sufficient for dual-run and conformance scaffolding.
+
+## Conformance harness scaffold
+
+```task
+id: HUB-WP-0004-T05
+status: todo
+priority: medium
+```
+
+Scaffold Tier 2/3 automated checks (schema validate, no-secrets, event family
+separation, projection rebuild fixture). Full green suite may continue under
+follow-on WPs.
+
+## Absorption plan with core-hub
+
+```task
+id: HUB-WP-0004-T06
+status: todo
+priority: high
+```
+
+With CORE-WP-0010, document route/module move order for `/api/v2`, dual-run, and
+cutover criteria. No big-bang.
+
+## Acceptance
+
+- [ ] Architecture freeze acknowledged in INTENT/SCOPE
+- [ ] Tier 1 contract artefacts published and versioned
+- [ ] Runtime packaging decision recorded
+- [ ] Core ports have a minimal implementable surface
+- [ ] Conformance harness scaffold exists
+- [ ] Absorption plan linked to CORE-WP-0010