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_test.go

@@ -220,6 +220,36 @@ topdata:
 	}
 }
 
+func TestEffectiveConfigIncludesTopDataRowExtensions(t *testing.T) {
+	root := t.TempDir()
+	writeProjectFile(t, filepath.Join(root, ConfigFile), `
+module:
+  name: Test Module
+  resref: testmod
+topdata:
+  source: topdata
+  row_extensions:
+    - dataset: classes/spellsgained/*
+      mode: repeat_last
+      level_column: Level
+      target_level: 60
+`)
+
+	proj, err := Load(root)
+	if err != nil {
+		t.Fatalf("Load returned error: %v", err)
+	}
+
+	rules := proj.EffectiveConfig().TopData.RowExtensions
+	if len(rules) != 1 {
+		t.Fatalf("expected one topdata row extension rule, got %#v", rules)
+	}
+	got := rules[0]
+	if got.Dataset != "classes/spellsgained/*" || got.Mode != "repeat_last" || got.LevelColumn != "Level" || got.TargetLevel != 60 {
+		t.Fatalf("unexpected topdata row extension rule: %#v", got)
+	}
+}
+
 func TestEffectiveConfigIncludesTopDataClassFeatInjections(t *testing.T) {
 	root := t.TempDir()
 	writeProjectFile(t, filepath.Join(root, ConfigFile), `
@@ -288,6 +318,11 @@ func TestValidateLayoutRejectsInvalidTopDataValueEncodings(t *testing.T) {
 					{Mode: "first_null_row"},
 					{Dataset: "classes", Mode: "first_null_row", MinimumRow: -1},
 				},
+				RowExtensions: []TopDataRowExtensionConfig{
+					{Dataset: "classes/spellsgained/*", Mode: "repeat_last", LevelColumn: "Level", TargetLevel: 60},
+					{Dataset: "classes/spellsgained/*", Mode: "repeat_last", LevelColumn: "Level", TargetLevel: 60},
+					{Dataset: "", Mode: "unsupported", LevelColumn: "", TargetLevel: 0},
+				},
 			},
 		},
 	}
@@ -311,6 +346,11 @@ func TestValidateLayoutRejectsInvalidTopDataValueEncodings(t *testing.T) {
 		"topdata.row_generation[2].mode \"unsupported\" is not supported",
 		"topdata.row_generation[3].dataset is required",
 		"topdata.row_generation[4].minimum_row must be zero or greater",
+		"topdata.row_extensions[1] duplicates an earlier dataset row extension rule",
+		"topdata.row_extensions[2].dataset is required",
+		"topdata.row_extensions[2].mode \"unsupported\" is not supported",
+		"topdata.row_extensions[2].level_column is required",
+		"topdata.row_extensions[2].target_level must be greater than zero",
 	} {
 		if !strings.Contains(text, want) {
 			t.Fatalf("expected validation error %q, got %v", want, err)