feat: separate multiple validation errors across all reporters

- Standard: each error on its own indented line
- JSON: errors as an array instead of a single joined string
- SARIF: each error as its own result entry for per-error annotations
- JUnit: each error on its own line within the failure message

Add SchemaErrors type to carry individual error messages from
JSONSchemaValidate, ValidateXSD, and SARIF schema validation.
The CLI populates ValidationErrors slice on Report for reporters
to consume.

Author: kehoecj

cmd/validator/testdata/json_schema.txtar

@@ -11,7 +11,7 @@ stdout '✓'
 # Invalid package.json (version must be string)
 ! exec validator invalid_package.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --- tsconfig.json schema ---
 
@@ -22,7 +22,7 @@ stdout '✓'
 # Invalid tsconfig.json (target must be string)
 ! exec validator invalid_tsconfig.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --- eslintrc schema ---
 
@@ -39,7 +39,7 @@ stdout '✓'
 # Invalid workflow (missing required jobs)
 ! exec validator invalid_workflow.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --- Strict config schema ---
 
@@ -50,27 +50,27 @@ stdout '✓'
 # Missing required field
 ! exec validator missing_required.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Wrong type
 ! exec validator wrong_type.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Extra property not allowed
 ! exec validator extra_property.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Value out of range
 ! exec validator out_of_range.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Enum violation
 ! exec validator bad_enum.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --- Array schema ---
 
@@ -81,12 +81,12 @@ stdout '✓'
 # Too few items
 ! exec validator too_few_items.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Wrong item type
 ! exec validator wrong_item_type.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --- Mixed: files with and without $schema ---
 

cmd/validator/testdata/no_schema.txtar

@@ -6,7 +6,7 @@ stdout '✓'
 # Without --no-schema it fails
 ! exec validator bad_with_schema.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --no-schema with YAML schema comment — skips validation
 exec validator --no-schema bad_with_schema.yaml

cmd/validator/testdata/schema_map.txtar

@@ -5,7 +5,7 @@ stdout '✓'
 # --schema-map with invalid data fails
 ! exec validator --schema-map=bad.json:schema.json bad.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # --schema-map with glob pattern
 exec validator --schema-map=**/*.json:schema.json subdir/config.json

cmd/validator/testdata/schemastore.txtar

@@ -14,7 +14,7 @@ stdout '✓'
 # Invalid package.json (version must be string)
 ! exec validator --schemastore schemastore invalid/package.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Valid nodemon.json
 exec validator --schemastore schemastore valid/nodemon.json
@@ -23,7 +23,7 @@ stdout '✓'
 # Invalid nodemon.json (unknown field, additionalProperties: false)
 ! exec validator --schemastore schemastore invalid/nodemon.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 2: --schemastore automatic matching (YAML)
@@ -36,7 +36,7 @@ stdout '✓'
 # Invalid GitHub workflow (missing required 'jobs')
 ! exec validator --schemastore schemastore invalid/.github/workflows/ci.yml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # Valid artifacthub-repo.yml
 exec validator --schemastore schemastore valid/artifacthub-repo.yml
@@ -45,7 +45,7 @@ stdout '✓'
 # Invalid artifacthub-repo.yml (additionalProperties: false)
 ! exec validator --schemastore schemastore invalid/artifacthub-repo.yml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 3: --schemastore automatic matching (TOML)
@@ -58,7 +58,7 @@ stdout '✓'
 # Invalid stylua.toml (column_width must be integer)
 ! exec validator --schemastore schemastore invalid/stylua.toml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 4: --schemastore automatic matching (TOON)
@@ -71,7 +71,7 @@ stdout '✓'
 # Invalid app.toon (port out of range)
 ! exec validator --schemastore schemastore invalid/app.toon
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 5: Unmatched files pass syntax-only
@@ -115,7 +115,7 @@ stdout '✓'
 # schema-map points to strict schema that rejects the file
 ! exec validator --schema-map=package.json:strict_schema.json --schemastore schemastore valid/package.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 9: --schema-map with YAML
@@ -126,7 +126,7 @@ stdout '✓'
 
 ! exec validator --schema-map=config.yaml:server_schema.json invalid/config.yaml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 10: --schema-map with TOML
@@ -137,7 +137,7 @@ stdout '✓'
 
 ! exec validator --schema-map=config.toml:server_schema.json invalid/config.toml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 11: --schema-map with TOON
@@ -148,7 +148,7 @@ stdout '✓'
 
 ! exec validator --schema-map=config.toon:server_schema.json invalid/config.toon
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 12: --schema-map with glob patterns
@@ -159,7 +159,7 @@ stdout '✓'
 
 ! exec validator --schema-map=**/configs/*.json:server_schema.json invalid/configs/db.json
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # PART 13: Multiple files, mixed results

cmd/validator/testdata/toml_schema.txtar

@@ -5,7 +5,7 @@ stdout '✓'
 # TOML with invalid data fails schema validation
 ! exec validator invalid.toml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # TOML without $schema passes (syntax only)
 exec validator plain.toml

cmd/validator/testdata/toon_schema.txtar

@@ -5,7 +5,7 @@ stdout '✓'
 # TOON with invalid data fails schema validation
 ! exec validator invalid.toon
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # TOON without $schema passes (syntax only)
 exec validator plain.toon

cmd/validator/testdata/xml_schema.txtar

@@ -61,7 +61,7 @@ stdout '✓'
 # Invalid type
 ! exec validator xsd_invalid.xml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # No schema passes syntax-only
 exec validator plain.xml
@@ -87,7 +87,7 @@ stdout '✓'
 # --schema-map with XSD invalid
 ! exec validator --schema-map=mapped_bad.xml:schema.xsd mapped_bad.xml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # ============================================================
 # DTD + XSD together
@@ -100,7 +100,7 @@ stdout '✓'
 # DTD valid but XSD fails (wrong type)
 ! exec validator dtd_ok_xsd_bad.xml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # DTD fails (missing element) — never reaches XSD
 ! exec validator dtd_bad_xsd_ok.xml

cmd/validator/testdata/yaml_schema.txtar

@@ -5,7 +5,7 @@ stdout '✓'
 # YAML with invalid data fails schema validation
 ! exec validator invalid.yaml
 stdout '×'
-stdout 'schema validation failed'
+stdout 'error:'
 
 # YAML without schema comment passes (syntax only)
 exec validator plain.yaml

pkg/cli/cli.go

@@ -130,14 +130,23 @@ func (c CLI) Run() (int, error) {
 			col = ve.Column
 		}
 
+		var validationErrors []string
+		var se *validator.SchemaErrors
+		if errors.As(err, &se) {
+			validationErrors = se.Errors()
+		} else if err != nil {
+			validationErrors = []string{err.Error()}
+		}
+
 		report := reporter.Report{
-			FileName:        fileToValidate.Name,
-			FilePath:        fileToValidate.Path,
-			IsValid:         isValid,
-			ValidationError: err,
-			IsQuiet:         Quiet,
-			StartLine:       line,
-			StartColumn:     col,
+			FileName:         fileToValidate.Name,
+			FilePath:         fileToValidate.Path,
+			IsValid:          isValid,
+			ValidationError:  err,
+			ValidationErrors: validationErrors,
+			IsQuiet:          Quiet,
+			StartLine:        line,
+			StartColumn:      col,
 		}
 		if !isValid {
 			errorFound = true

pkg/reporter/json_reporter.go

@@ -17,9 +17,9 @@ func NewJSONReporter(outputDest string) *JSONReporter {
 }
 
 type fileStatus struct {
-	Path   string `json:"path"`
-	Status string `json:"status"`
-	Error  string `json:"error,omitempty"`
+	Path   string   `json:"path"`
+	Status string   `json:"status"`
+	Errors []string `json:"errors,omitempty"`
 }
 
 type summary struct {
@@ -202,10 +202,10 @@ func createJSONReport(reports []Report) (reportJSON, error) {
 
 	for _, report := range reports {
 		status := "passed"
-		errorStr := ""
+		var errs []string
 		if !report.IsValid {
 			status = "failed"
-			errorStr = report.ValidationError.Error()
+			errs = report.ValidationErrors
 		}
 
 		// Convert Windows-style file paths.
@@ -216,7 +216,7 @@ func createJSONReport(reports []Report) (reportJSON, error) {
 		jsonReport.Files = append(jsonReport.Files, fileStatus{
 			Path:   report.FilePath,
 			Status: status,
-			Error:  errorStr,
+			Errors: errs,
 		})
 
 		currentPassed := 0