Automatic spellknown/spellgain null-filling (#12)

Implemented on branches `feature/topdata-row-extensions` in both `toolkit` and `module`.

**Scope Audited**
- Toolkit native topdata collection/build path.
- Project config/effective config validation.
- Module `nwn-tool.yaml` topdata config and topdata README.

**Changes Made**
- Added `topdata.row_extensions` config with `repeat_last` support.
- Added glob dataset matching and build-time row extension for plain native datasets in [native.go](/home/vicky/Projects/nwnee-shadowsoverwestgate/toolkit/internal/topdata/native.go:641).
- Extension copies emitted columns from the highest authored `Level`, increments `Level`, and assigns sequential `id`s through target level.
- Enabled rules for `classes/spellsgained/*` and `classes/spellsknown/*` to level 60 in [nwn-tool.yaml](/home/vicky/Projects/nwnee-shadowsoverwestgate/module/nwn-tool.yaml:90).
- Updated toolkit/module docs.

**Configuration / Compatibility**
- New public config type: `TopDataRowExtensionConfig` in [project.go](/home/vicky/Projects/nwnee-shadowsoverwestgate/toolkit/internal/project/project.go:233).
- Existing behavior is unchanged unless a repo opts into `topdata.row_extensions`.
- Source JSON and lockfiles are not updated for generated extension rows.

**Tests / Validation**
- Added project config tests for loading and validation.
- Added native topdata tests for extension behavior, glob application, preserving manually authored rows, unmatched datasets, and failure cases.
- Ran:
  - `go test ./internal/project ./internal/topdata`
  - `go test ./internal/topdata -run TestBuildNativeKeepsGeneratedIDsStableAcrossRepeatedBuilds`
  - `/tmp/sow-toolkit-rowext config validate` in `module`
  - `/tmp/sow-toolkit-rowext validate-topdata` in `module`
  - `/tmp/sow-toolkit-rowext build-topdata --force`, then inspected generated rows: `cls_spgn_acolyte.2da` now reaches row `59` / level `60`.

**Remaining Notes**
- `validate-topdata` still reports the pre-existing portrait lock warnings for `cotbl/cotbl_` and `lantern/lantern_`.
- `build-topdata --force` briefly rewrote three spellbook JSON files as a side effect; I reverted those, leaving only the intended YAML/docs changes in `module`.

Reviewed-on: https://gitea.westgate.pw/ShadowsOverWestgate/sow-tools/pulls/12
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

internal/project/project.go

@@ -218,6 +218,7 @@ type TopDataConfig struct {
 	ValueEncodings      []TopDataValueEncodingConfig    `json:"value_encodings" yaml:"value_encodings"`
 	ValueDefaults       []TopDataValueDefaultConfig     `json:"value_defaults" yaml:"value_defaults"`
 	RowGeneration       []TopDataRowGenerationConfig    `json:"row_generation" yaml:"row_generation"`
+	RowExtensions       []TopDataRowExtensionConfig     `json:"row_extensions" yaml:"row_extensions"`
 	ClassFeatInjections TopDataClassFeatInjectionConfig `json:"class_feat_injections" yaml:"class_feat_injections"`
 	Wiki                TopDataWikiConfig               `json:"wiki" yaml:"wiki"`
 }
@@ -229,6 +230,13 @@ type TopDataRowGenerationConfig struct {
 	MinimumRow int    `json:"minimum_row,omitempty" yaml:"minimum_row,omitempty"`
 }
 
+type TopDataRowExtensionConfig struct {
+	Dataset     string `json:"dataset" yaml:"dataset"`
+	Mode        string `json:"mode" yaml:"mode"`
+	LevelColumn string `json:"level_column" yaml:"level_column"`
+	TargetLevel int    `json:"target_level" yaml:"target_level"`
+}
+
 type TopDataClassFeatInjectionConfig struct {
 	GlobalFeats           []TopDataClassFeatGlobalRule     `json:"global_feats" yaml:"global_feats"`
 	ClassSkillMasterfeats []TopDataClassFeatMasterfeatRule `json:"class_skill_masterfeats" yaml:"class_skill_masterfeats"`
@@ -631,6 +639,7 @@ func (p *Project) ValidateLayout() error {
 	failures = append(failures, validateTopDataValueEncodings(effective.TopData.ValueEncodings)...)
 	failures = append(failures, validateTopDataValueDefaults(effective.TopData.ValueDefaults)...)
 	failures = append(failures, validateTopDataRowGeneration(effective.TopData.RowGeneration)...)
+	failures = append(failures, validateTopDataRowExtensions(effective.TopData.RowExtensions)...)
 	failures = append(failures, validateTopDataClassFeatInjections(effective.TopData.ClassFeatInjections)...)
 	failures = append(failures, validateRelativePath("scripts.cache", effective.Scripts.Cache)...)
 	failures = append(failures, validateRelativePath("scripts.source_dir", effective.Scripts.SourceDir)...)
@@ -873,6 +882,35 @@ func validateTopDataRowGeneration(rules []TopDataRowGenerationConfig) []error {
 	return failures
 }
 
+func validateTopDataRowExtensions(rules []TopDataRowExtensionConfig) []error {
+	failures := []error{}
+	seen := map[string]struct{}{}
+	for index, rule := range rules {
+		prefix := fmt.Sprintf("topdata.row_extensions[%d]", index)
+		dataset := strings.TrimSpace(rule.Dataset)
+		if dataset == "" {
+			failures = append(failures, fmt.Errorf("%s.dataset is required", prefix))
+		}
+		switch strings.TrimSpace(rule.Mode) {
+		case "repeat_last":
+		default:
+			failures = append(failures, fmt.Errorf("%s.mode %q is not supported", prefix, rule.Mode))
+		}
+		if strings.TrimSpace(rule.LevelColumn) == "" {
+			failures = append(failures, fmt.Errorf("%s.level_column is required", prefix))
+		}
+		if rule.TargetLevel <= 0 {
+			failures = append(failures, fmt.Errorf("%s.target_level must be greater than zero", prefix))
+		}
+		key := filepath.ToSlash(dataset)
+		if _, ok := seen[key]; ok {
+			failures = append(failures, fmt.Errorf("%s duplicates an earlier dataset row extension rule", prefix))
+		}
+		seen[key] = struct{}{}
+	}
+	return failures
+}
+
 func validateTopDataClassFeatInjections(config TopDataClassFeatInjectionConfig) []error {
 	failures := []error{}
 	for index, rule := range config.GlobalFeats {