Adapt specs and workplans to SWOT Stage 0 sequencing

Introduce SCOPE, expanded README, CONTRIBUTING, and provisional open-question
defaults. Rescope Trust Service work to offline schemas/fold/fixtures, add
normative core extraction workplan, and split PRD roadmap Phase 4 into
foundation vs hosted service. Sync workplans with State Hub.

CONTRIBUTING.md

@@ -0,0 +1,46 @@
+# Contributing to target-revenue
+
+## Repository status
+
+This repository defines a **framework concept and specifications**. It does not yet provide a production-ready Target Revenue Source License (TRSL) or a production Trust Service.
+
+**Do not** use draft TRSL language to govern production software or accept customer commercial entitlements under TRF until specialist legal review is complete and SCOPE says otherwise.
+
+## What contributions are welcome now
+
+| Kind | Guidance |
+| --- | --- |
+| Spec and doc improvements | Preferred: clarity, consistency with core terms, open-question research, examples |
+| Schemas, pure fold, validators, golden fixtures | Preferred once workplans WP-0002 / WP-0003 are active |
+| Prior-art research notes | Prefer updating or linking from WP-0001 deliverables |
+| Implementation of a full hosted Trust Service | Out of scope until SCOPE sequencing rules are met |
+
+## Terminology
+
+Use the normative terms from `spec/TargetRevenueLicenseConcept.md` §7. Do **not** reintroduce ambiguous synonyms for conversion metrics (e.g. treating total project “revenue captured” as equivalent to Development Credit).
+
+Pre-conversion software is **source-available**, not OSI Open Source.
+
+## External contributions and governed code
+
+**External contributions are not accepted into any governed Milestone Release** until a contributor-rights instrument (CLA, assignment, or equivalent inbound grant covering both TRSL phase and Future License) is adopted.
+
+Documentation-only and schema-only contributions to *this* framework repository may be accepted under the repository LICENSE without that instrument, at maintainer discretion.
+
+A Developer Certificate of Origin (DCO) alone is **not** assumed sufficient for dual-phase relicensing of product code; see open questions and WP-0001-T04.
+
+## Human decision gates
+
+The following must not be marked complete by agents alone without explicit human accept (comment, decision record, or maintainer message):
+
+- Non-binding TRSL draft skeleton (WP-0001-T06)
+- Library/stack ADR that locks implementation technology (WP-0002-T01)
+- Promotion of working defaults into normative core wording
+
+## Workplans
+
+Prefer small, hub-linked workplan tasks. Do not register workplans only in the State Hub; write the workplan file under `workplans/` and run consistency sync so local files remain source of truth.
+
+## Questions
+
+Start from `README.md` reading order and `SCOPE.md`. Unresolved product questions live in the PRD §14 and `specs/OpenQuestions-WorkingDefaults.md`.