Document translation catalog structure

Signed-off-by: Loren Eteval <loren.eteval@proton.me>

Furious/Externals/AGENTS.md

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+# Translation catalog guidance
+
+These instructions apply to `Furious/Externals/` and refine the repository-level generated-artifact and translation
+rules.
+
+## Generated catalog ownership
+
+- `GenTranslation.py` is generated by the repository-root `Translation.py`; do not hand-maintain catalog entries for
+  routine source changes.
+- Add or change extracted source strings at their call sites, run the translation generator for every supported
+  language, review the translations, and regenerate the catalog.
+- If generated record structure or key ordering needs correction, fix `Translation.py` rather than applying a one-off
+  rewrite to `GenTranslation.py`.
+
+## Translation record structure
+
+- `TRANSLATION` maps each exact English source string to one record.
+- `source` is the generator-maintained list of fully qualified modules where that string is extracted.
+- Each supported non-English language has one abbreviation key, such as `RU` or `ZH`, whose value is the reviewed
+  user-facing translation.
+- `isReviewed` is the string `"True"` or `"False"`, not a JSON/Python boolean. Mark it `"True"` only after every
+  language value in the record has been reviewed.
+- Preserve this preferred serialized key sequence in every record: `source`, language 1, language 2, ..., `isReviewed`.
+  Keep `source` first and `isReviewed` last; use the catalog's stable language order between them.
+- Do not add ad-hoc metadata fields that the generator and runtime do not understand.
+
+For example:
+
+```python
+"Delete": {
+    "source": [
+        "Furious.Backends...",
+        "Furious.Backends...",
+    ],
+    "RU": "Удалить",
+    "ZH": "删除",
+    "isReviewed": "True"
+}
+```
+
+## Extraction and review rules
+
+- Keep translation source keys as literal strings discoverable by the existing `_()` extractor. Do not pass formatted
+  strings, f-strings, or `.format(...)` results to `_()`.
+- Braces in extracted strings are reserved for application-constant substitution by `Translation.py`; they are not
+  general runtime-format placeholders.
+- Let the generator derive `source`; do not fabricate or retain stale module names manually.
+- Review natural terminology and meaning in every supported language, not only literal word correspondence. Do not
+  approve source-language placeholders as completed translations.
+
+## Code review rules
+
+- Flag direct catalog edits that should have been made through source extraction and regeneration.
+- Flag records whose key sequence is not `source`, language keys, then `isReviewed`.
+- Flag `"isReviewed": "True"` when any language is missing or unreviewed.
+- Flag dynamic formatting inside `_()` and changes that treat braces as ordinary formatting syntax.