chore: BL-15916 separate raw source data files from processed data files

https://issues.bloomlibrary.org/youtrack/issue/BL-15916

The card notes that the raw source files and the files our pipeline generates
from them lived together in one folder and should be separated. Move the raw
source files into a new language-data/source/ subfolder, leaving the generated
files (languageData.json, equivalentTags.json), which the runtime imports, in
language-data/:

- language-data/source/langtags.json
- language-data/source/iso-639-3.tab
- language-data/source/iso-639-3-macrolanguages.tab

Updated the source-file import/read paths in langtagProcessing.ts and
langtagProcessingHelpers.ts, and the Data sources section of the README.

Verified: re-running the langtag-processing pipeline from the new paths
produces byte-identical languageData.json and equivalentTags.json; tsc
typecheck passes; the full find-language test suite passes (174/174).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: andrew-polk

components/language-chooser/common/find-language/README.md

@@ -206,7 +206,7 @@ For languages that are representative for a macrolanguage, however, we use the i
 
 ## Data sources
 
-We get our data from the [langtags repository](https://github.com/silnrsi/langtags/tree/master) and [ISO 639-3](https://iso639-3.sil.org/). All live in the [language-data](./language-data/) folder. In the future, we plan to automate the update of these data files, but currently it is done manually.
+We get our raw source data from the [langtags repository](https://github.com/silnrsi/langtags/tree/master) and [ISO 639-3](https://iso639-3.sil.org/). These raw files live in the [language-data/source](./language-data/source/) folder, kept separate from the processed files (see below) that our pipeline generates from them. In the future, we plan to automate the update of these data files, but currently it is done manually.
 
 - langtags.json
   - source: https://ldml.api.sil.org/langtags.json
@@ -218,7 +218,7 @@ We get our data from the [langtags repository](https://github.com/silnrsi/langta
   - source: https://iso639-3.sil.org/sites/iso639-3/files/downloads/iso-639-3-macrolanguages.tab
   - documentation: https://iso639-3.sil.org/code_tables/download_tables
 
-Currently also in the folder, data files compiled by our language data processing (see section above):
+The processed data files compiled by our language data processing (see section above) live in the [language-data](./language-data/) folder:
 
 - languageData.json
 - equivalentTags.json

…nguage-data/iso-639-3-macrolanguages.tab …data/source/iso-639-3-macrolanguages.tabcomponents/language-chooser/common/find-language/language-data/iso-639-3-macrolanguages.tab renamed to components/language-chooser/common/find-language/language-data/source/iso-639-3-macrolanguages.tab components/language-chooser/common/find-language/language-data/iso-639-3-macrolanguages.tab renamed to components/language-chooser/common/find-language/language-data/source/iso-639-3-macrolanguages.tab

@@ -18,7 +18,7 @@ import {
 } from "./langtagProcessingHelpers";
 
 import fs from "fs";
-import langTagsJson from "../language-data/langtags.json" with { type: "json" };
+import langTagsJson from "../language-data/source/langtags.json" with { type: "json" };
 
 function bestAutonymFromEntry(entry: any) {
   return entry.localnames ? entry.localnames[0] : entry.localname;

…ind-language/language-data/iso-639-3.tab …guage/language-data/source/iso-639-3.tabcomponents/language-chooser/common/find-language/language-data/iso-639-3.tab renamed to components/language-chooser/common/find-language/language-data/source/iso-639-3.tab components/language-chooser/common/find-language/language-data/iso-639-3.tab renamed to components/language-chooser/common/find-language/language-data/source/iso-639-3.tab

@@ -1,5 +1,5 @@
 import { iso15924 } from "iso-15924";
-import langTagsJson from "../language-data/langtags.json" with { type: "json" };
+import langTagsJson from "../language-data/source/langtags.json" with { type: "json" };
 import fs from "fs";
 import { ILanguage, IScript, LanguageType } from "../findLanguageInterfaces";
 import {
@@ -78,7 +78,7 @@ export const scriptNames: { [key: string]: string } = iso15924.reduce(
                                     -- E(xtinct), H(istorical), L(iving), S(pecial)
 */
 const isoCodesDetailsFile = fs.readFileSync(
-  "language-data/iso-639-3.tab",
+  "language-data/source/iso-639-3.tab",
   "utf8"
 );
 
@@ -140,7 +140,7 @@ for (const line of isoCodesDetailsFile.split("\n")) {
 }
 
 const macrolangMappingFile = fs.readFileSync(
-  "language-data/iso-639-3-macrolanguages.tab",
+  "language-data/source/iso-639-3-macrolanguages.tab",
   "utf8"
 );
 export const indivlangsToMacrolangs: { [key: string]: string } = {};