Add phased knowledge layer: comments and semantic linking pipeline

backend/src/knowledge/dto/semantic-link.dto.ts

@@ -0,0 +1,52 @@
+import { IsIn, IsNumber, IsObject, IsOptional, IsString, Max, Min } from 'class-validator';
+
+export const SEMANTIC_LINK_STATUSES = ['suggested', 'approved', 'rejected', 'dismissed'] as const;
+export const SEMANTIC_LINK_ORIGINS = ['manual', 'semantic', 'llm', 'hybrid', 'rule_based'] as const;
+
+export class ReviewSemanticLinkDto {
+  @IsString()
+  @IsIn(SEMANTIC_LINK_STATUSES)
+  status: (typeof SEMANTIC_LINK_STATUSES)[number];
+}
+
+export class UpsertSemanticLinkDto {
+  @IsString()
+  sourceEntityType: string;
+
+  @IsString()
+  sourceEntityId: string;
+
+  @IsString()
+  targetEntityType: string;
+
+  @IsString()
+  targetEntityId: string;
+
+  @IsOptional()
+  @IsString()
+  linkType?: string;
+
+  @IsOptional()
+  @IsString()
+  @IsIn(SEMANTIC_LINK_STATUSES)
+  status?: (typeof SEMANTIC_LINK_STATUSES)[number];
+
+  @IsOptional()
+  @IsString()
+  @IsIn(SEMANTIC_LINK_ORIGINS)
+  origin?: (typeof SEMANTIC_LINK_ORIGINS)[number];
+
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  @Max(1)
+  confidence?: number;
+
+  @IsOptional()
+  @IsString()
+  reason?: string;
+
+  @IsOptional()
+  @IsObject()
+  evidence?: Record<string, any>;
+}