fix(topdata): encode spell radial feat IDs (#37)

## Summary
- add explicit `{"spellradial": {"id": "feat:key"}}` authoring syntax for `spells.2da` `FeatID`
- resolve spell and feat rows dynamically and emit NWN:EE packed subradial values
- reject malformed or misplaced spell-radial references

## Verification
- `go test ./internal/topdata`

Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Reviewed-on: #37
Reviewed-by: archvillainette <vickydotbat@tutamail.com>
Reviewed-by: xtul <mpiasecki720@protonmail.com>
Co-authored-by: gitea-bot <gitea-bot@noreply.git.westgate.pw>
Co-committed-by: gitea-bot <gitea-bot@noreply.git.westgate.pw>

internal/topdata/topdata_test.go

@@ -11887,7 +11887,7 @@ func TestBuildSupportsCanonicalSpells(t *testing.T) {
     "spells:disarm": {
       "Label": "Disarm",
       "Name": "501",
-      "FeatID": {"id": "feat:disarm"},
+      "FeatID": {"spellradial": {"id": "feat:specialattacks"}},
       "Master": {"id": "spells:specialattacks"},
       "Category": {"ref": "spells:specialattacks", "field": "Category"}
     }
@@ -11939,7 +11939,7 @@ func TestBuildSupportsCanonicalSpells(t *testing.T) {
 		!strings.Contains(text, "\t1000\t") ||
 		!strings.Contains(text, "841\tDisarm\t501") ||
 		!strings.Contains(text, "\t840\t") ||
-		!strings.Contains(text, "\t1001\t") ||
+		!strings.Contains(text, "\t55116776\t") ||
 		!strings.Contains(text, "849\tBard_Fascinate\t600") ||
 		!strings.Contains(text, "\t601\t") ||
 		!strings.Contains(text, "\t602\t") ||