docs: add ADR for evidence fabric boundaries and contract ownership

docs/adr/0006-evidence-fabric-boundaries.md

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+# ADR-0006: Evidence Fabric Boundaries and Contract Ownership
+
+**Status:** Proposed  
+**Date:** 2026-04-09  
+**Deciders:** SourceOS core team
+
+---
+
+## Context
+
+`sourceos-spec` already defines the umbrella metadata-plane and governance vocabulary for SourceOS/SociOS. Existing first-class semantic concepts include dataset, field, policy, workflow specification, run record, agreement, glossary terms, and related contract families.
+
+At the same time, the broader platform now needs a distinct evidence fabric for ingesting and preserving large mixed-format corpora from local disks and external drives such as Google Drive and iCloud Drive.
+
+Without an explicit boundary, the following risks emerge:
+
+- the metadata plane absorbs operational evidence-custody contracts and becomes muddled,
+- the evidence plane redefines governance and provenance concepts that should remain canonical at the SourceOS metadata-plane level,
+- desktop integration, storage, and runtime broker work blur together.
+
+This ADR freezes the boundary.
+
+## Decision
+
+### 1. `sourceos-spec` remains the umbrella metadata-plane contract layer
+
+`sourceos-spec` SHALL continue to own:
+
+- top-level semantic context and JSON-LD/Hydra overlays,
+- generic governance and policy vocabulary,
+- provenance and agreement families,
+- workflow and run-record umbrella semantics,
+- connector/asset/schema families at the metadata-plane level.
+
+It SHALL NOT become the direct implementation home for the operational evidence-plane runtime contracts.
+
+### 2. The evidence fabric becomes a distinct operational contract family
+
+A separate evidence-plane contract family SHALL be implemented in a dedicated SocioProphet repo family.
+
+The initial evidence-plane object families are expected to include:
+
+- `ConnectorProfile`
+- `AcquisitionRun`
+- `EvidenceBlob`
+- `EvidenceItem`
+- `EvidenceEntity`
+- `EvidenceEvent`
+- `ParserRun`
+- `ValidationResult`
+
+These names are intentionally distinct from existing `sourceos-spec` umbrella names such as `RunRecord`.
+
+### 3. Reserved boundaries
+
+The following semantic names remain reserved to the existing umbrella or adjacent systems and SHOULD NOT be reused as canonical evidence-plane runtime object names:
+
+- `Dataset`
+- `Field`
+- `Policy`
+- `WorkflowSpec`
+- `RunRecord`
+- `Agreement`
+- `GlossaryTerm`
+
+Likewise, traversal-native names owned by the CairnPath family SHOULD NOT be reused for evidence runtime objects:
+
+- `Context`
+- `Step`
+- `Line`
+- `Result`
+- `Materialize`
+
+### 4. `kind` not `type` for operational evidence contracts
+
+Operational evidence-plane contracts SHOULD use `kind` as their runtime discriminator rather than `type`.
+
+Rationale:
+
+- `type` is already semantically overloaded in JSON-LD style overlays and metadata-plane contexts,
+- `kind` avoids ambiguity between runtime contract discrimination and semantic linked-data typing.
+
+### 5. Repo ownership split
+
+#### SourceOS-Linux
+
+SourceOS-Linux SHALL own umbrella metadata-plane, governance, and semantic overlay contracts.
+
+#### SocioProphet
+
+SocioProphet SHALL own the operational evidence-plane implementation repos, including the planned families:
+
+- `evidence-contracts`
+- `evidence-broker`
+- `evidence-connectors-gdrive`
+- `evidence-connectors-icloud`
+- `evidence-validator`
+- `evidence-storage-infra`
+
+#### SociOS-Linux
+
+SociOS-Linux SHALL own desktop-facing account UX, mounted filesystem surfaces, operator-facing file access, and local capture pathways.
+
+## Consequences
+
+### Positive
+
+- the metadata plane remains clean and composable,
+- the evidence plane can move quickly without redefining SourceOS governance primitives,
+- connector/runtime/storage work can be implemented in SocioProphet without polluting the semantic overlay layer,
+- desktop and operator surfaces remain free to evolve in SociOS-Linux.
+
+### Negative
+
+- cross-repo coordination is mandatory,
+- some provenance and connector concepts will need explicit mapping between `sourceos-spec` and the evidence-plane contract set,
+- implementation cannot rely on a single monorepo or one oversized schema package.
+
+## Required interoperability rule
+
+All evidence-plane repos SHALL align upward to `sourceos-spec` for umbrella governance and provenance semantics, but SHALL keep their runtime object names and schemas in the dedicated evidence-plane contract family.
+
+In short:
+
+**`sourceos-spec` defines the umbrella metadata plane; the evidence fabric implements custody and normalization beneath it.**