Add evidence context artifact builder

internal/framework/evidencecontext/model.go

@@ -0,0 +1,50 @@
+// Package evidencecontext owns the durable source evidence-context contract.
+package evidencecontext
+
+import (
+	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
+)
+
+const (
+	ArtifactKind  contracts.ArtifactKind = "source/evidence-context"
+	SchemaID                             = "notarius.source.evidence_context"
+	SchemaName                           = "notarius_source_evidence_context_v1"
+	SchemaVersion                        = "v1"
+	MediaType                            = "application/json"
+)
+
+// Document is the durable union of direct evidence and surrounding source
+// context selected for one accepted source document.
+type Document struct {
+	SourceID      string    `json:"source_id"`
+	SourceDigest  string    `json:"source_digest"`
+	WindowUnits   int       `json:"window_units"`
+	SelectedLanes []string  `json:"selected_lanes"`
+	Contexts      []Context `json:"contexts"`
+}
+
+type Context struct {
+	ContextRef   source.SourceRef    `json:"context_ref"`
+	EvidenceRefs []EvidenceRef       `json:"evidence_refs"`
+	Units        []source.SourceUnit `json:"units"`
+}
+
+type EvidenceRef struct {
+	LaneID    string           `json:"lane_id"`
+	SourceRef source.SourceRef `json:"source_ref"`
+}
+
+// LaneEvidence attributes direct source references to one selected lane.
+type LaneEvidence struct {
+	LaneID     string             `json:"lane_id"`
+	SourceRefs []source.SourceRef `json:"source_refs"`
+}
+
+// BuildRequest supplies accepted source material and direct lane evidence.
+type BuildRequest struct {
+	Source        *source.SourceDocument
+	WindowUnits   int
+	SelectedLanes []string
+	LaneEvidence  []LaneEvidence
+}