Generate contract types, pin fixtures to spec, add build and ADRs

Completes FLUID-WP-0002. The record types in internal/contract are
generated from schemas/ by a dependency-free generator; fixtures
transcribed from the spec's worked examples validate against those
schemas and round-trip through the generated types with
DisallowUnknownFields, so a spec change that misses the schemas fails
CI rather than drifting silently.

Adds identifier prefix helpers, Makefile, GitHub Actions, and five ADRs
recording the Go choice, out-of-process attachment, the wire contract as
boundary, the evidence store, and revision identity.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014KmVxhJ35tCo7rE7UnLwWu

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1116572@bnt-lap001
Assistant-Session: 8ba9bb93-a72a-4883-b189-2499cce5c400

internal/contract/backend_requirement_gen.go

@@ -0,0 +1,100 @@
+// Code generated by tools/schemagen. DO NOT EDIT.
+// Source: schemas/. Regenerate with `make generate`.
+
+package contract
+
+type FluidBackendRequirementCapability struct {
+	Description string `json:"description" yaml:"description"`
+	Title       string `json:"title" yaml:"title"`
+}
+
+type FluidBackendRequirementDispositionState string
+
+const (
+	FluidBackendRequirementDispositionStateOPEN               FluidBackendRequirementDispositionState = "OPEN"
+	FluidBackendRequirementDispositionStateACCEPTED           FluidBackendRequirementDispositionState = "ACCEPTED"
+	FluidBackendRequirementDispositionStatePLANNED            FluidBackendRequirementDispositionState = "PLANNED"
+	FluidBackendRequirementDispositionStateAVAILABLE          FluidBackendRequirementDispositionState = "AVAILABLE"
+	FluidBackendRequirementDispositionStatePARTIALLYAVAILABLE FluidBackendRequirementDispositionState = "PARTIALLY_AVAILABLE"
+	FluidBackendRequirementDispositionStateOUTOFSCOPE         FluidBackendRequirementDispositionState = "OUT_OF_SCOPE"
+	FluidBackendRequirementDispositionStateREJECTED           FluidBackendRequirementDispositionState = "REJECTED"
+	FluidBackendRequirementDispositionStateSUPERSEDED         FluidBackendRequirementDispositionState = "SUPERSEDED"
+)
+
+// Valid reports whether v is a defined FluidBackendRequirementDispositionState.
+func (v FluidBackendRequirementDispositionState) Valid() bool {
+	switch v {
+	case FluidBackendRequirementDispositionStateOPEN, FluidBackendRequirementDispositionStateACCEPTED, FluidBackendRequirementDispositionStatePLANNED, FluidBackendRequirementDispositionStateAVAILABLE, FluidBackendRequirementDispositionStatePARTIALLYAVAILABLE, FluidBackendRequirementDispositionStateOUTOFSCOPE, FluidBackendRequirementDispositionStateREJECTED, FluidBackendRequirementDispositionStateSUPERSEDED:
+		return true
+	}
+	return false
+}
+
+// The backend decides. Repeated OUT_OF_SCOPE feeds boundary learning
+// (ArchitectureBlueprint.md section 22).
+type FluidBackendRequirementDisposition struct {
+	Reason    *string                                 `json:"reason,omitempty" yaml:"reason,omitempty"`
+	State     FluidBackendRequirementDispositionState `json:"state" yaml:"state"`
+	TargetRef *string                                 `json:"target_ref,omitempty" yaml:"target_ref,omitempty"`
+}
+
+type FluidBackendRequirementExpectedUsage struct {
+	RequestsPerDay *int64 `json:"requests_per_day,omitempty" yaml:"requests_per_day,omitempty"`
+}
+
+type FluidBackendRequirementQuality struct {
+	Availability *UnitInterval `json:"availability,omitempty" yaml:"availability,omitempty"`
+	P95LatencyMS *float64      `json:"p95_latency_ms,omitempty" yaml:"p95_latency_ms,omitempty"`
+}
+
+type FluidBackendRequirementSecurity struct {
+	AuthorizationScope string `json:"authorization_scope,omitempty" yaml:"authorization_scope,omitempty"`
+	TenantIsolation    string `json:"tenant_isolation,omitempty" yaml:"tenant_isolation,omitempty"`
+}
+
+type FluidBackendRequirementSemantics struct {
+	Consistency    string   `json:"consistency,omitempty" yaml:"consistency,omitempty"`
+	RequiredFields []string `json:"required_fields,omitempty" yaml:"required_fields,omitempty"`
+}
+
+type FluidBackendRequirementUrgency string
+
+const (
+	FluidBackendRequirementUrgencyLOW    FluidBackendRequirementUrgency = "LOW"
+	FluidBackendRequirementUrgencyMEDIUM FluidBackendRequirementUrgency = "MEDIUM"
+	FluidBackendRequirementUrgencyHIGH   FluidBackendRequirementUrgency = "HIGH"
+)
+
+// Valid reports whether v is a defined FluidBackendRequirementUrgency.
+func (v FluidBackendRequirementUrgency) Valid() bool {
+	switch v {
+	case FluidBackendRequirementUrgencyLOW, FluidBackendRequirementUrgencyMEDIUM, FluidBackendRequirementUrgencyHIGH:
+		return true
+	}
+	return false
+}
+
+type FluidBackendRequirement struct {
+	BackendService string                            `json:"backend_service" yaml:"backend_service"`
+	Capability     FluidBackendRequirementCapability `json:"capability" yaml:"capability"`
+
+	// The backend decides. Repeated OUT_OF_SCOPE feeds boundary learning
+	// (ArchitectureBlueprint.md section 22).
+	Disposition           FluidBackendRequirementDisposition    `json:"disposition" yaml:"disposition"`
+	ExpectedUsage         *FluidBackendRequirementExpectedUsage `json:"expected_usage,omitempty" yaml:"expected_usage,omitempty"`
+	ID                    BackendRequirementID                  `json:"id" yaml:"id"`
+	OriginatingHypothesis *HypothesisID                         `json:"originating_hypothesis,omitempty" yaml:"originating_hypothesis,omitempty"`
+	OriginatingInterface  InterfaceID                           `json:"originating_interface" yaml:"originating_interface"`
+	OriginatingRevision   *RevisionID                           `json:"originating_revision,omitempty" yaml:"originating_revision,omitempty"`
+	Quality               *FluidBackendRequirementQuality       `json:"quality,omitempty" yaml:"quality,omitempty"`
+	SchemaVersion         SchemaVersion                         `json:"schema_version" yaml:"schema_version"`
+	Security              *FluidBackendRequirementSecurity      `json:"security,omitempty" yaml:"security,omitempty"`
+	Semantics             *FluidBackendRequirementSemantics     `json:"semantics,omitempty" yaml:"semantics,omitempty"`
+	Urgency               *FluidBackendRequirementUrgency       `json:"urgency,omitempty" yaml:"urgency,omitempty"`
+}
+
+// Capability the interface needs but has no authority to build. FLUID escalates
+// rather than crossing the boundary (FluidAPIStandards.md section 30).
+type BackendRequirementDocument struct {
+	FluidBackendRequirement FluidBackendRequirement `json:"fluid_backend_requirement" yaml:"fluid_backend_requirement"`
+}