docs: add parquet stale-artifact guard workflow

ADDING_NEW_UD_VERSION.md

@@ -225,13 +225,13 @@ cat blocked_treebanks.yaml
 
 ```bash
 # Test with 3 treebanks first
-uv run ./04_generate_parquet.py --ud-ver ${NEW_VER} --test
+uv run ./04_generate_parquet.py --ud-ver ${NEW_VER} --test --prune-extra --check-extra
 
 # If successful, generate all treebanks (takes 2-4 hours)
-uv run ./04_generate_parquet.py --ud-ver ${NEW_VER}
+uv run ./04_generate_parquet.py --ud-ver ${NEW_VER} --prune-extra --check-extra
 
 # Re-runs on an existing branch should overwrite in-place
-# uv run ./04_generate_parquet.py --ud-ver ${NEW_VER} --overwrite
+# uv run ./04_generate_parquet.py --ud-ver ${NEW_VER} --overwrite --prune-extra --check-extra
 
 # This creates:
 # - ../parquet/{treebank_name}/{split}.parquet for all treebanks
@@ -247,6 +247,11 @@ du -sh ../parquet/
 - `--test`: Generate only 3 treebanks (quick test)
 - `--overwrite`: Regenerate existing files
 - `--blocked-treebanks`: Path to YAML file with blocked treebanks
+- `--check-extra`: Fail fast if extra parquet files/directories are present
+- `--prune-extra`: Delete extra parquet files/directories before generation
+
+**Recommended release flags:** `--prune-extra --check-extra` to guard against
+stale parquet artifacts when treebanks are renamed/removed between UD versions.
 
 **Expected time:** 2-4 hours for all treebanks
 
@@ -449,7 +454,7 @@ for UD_VER in 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17; do
   uv run ./03_generate_README.py -o --ud-ver "${UD_VER}"
   cp "README-${UD_VER}" ../README.md
   cp "metadata-${UD_VER}.json" ../metadata.json
-  uv run ./04_generate_parquet.py --ud-ver "${UD_VER}" --overwrite
+  uv run ./04_generate_parquet.py --ud-ver "${UD_VER}" --overwrite --prune-extra --check-extra
   uv run ./05_validate_parquet.py --ud-ver "${UD_VER}" --local
   cd ..
 
@@ -560,6 +565,7 @@ Before marking the release as complete:
 - [ ] `metadata-{VER}.json` generated with blocked treebank info
 - [ ] `README-{VER}` generated
 - [ ] Parquet files generated for all non-blocked treebanks
+- [ ] Parquet run used stale-artifact guard (`--prune-extra --check-extra`)
 - [ ] Full local validation run (`--local` without `--test`)
 - [ ] Root files synced from tools outputs before parquet generation and before commit
 - [ ] Files copied to repository root (`README.md`, `metadata.json`, `parquet/`)

tools/README.md

@@ -25,7 +25,7 @@ cp README-${NEW_VER} ../README.md
 cp metadata-${NEW_VER}.json ../metadata.json
 
 # Generate and fully validate parquet
-uv run 04_generate_parquet.py --ud-ver "${NEW_VER}"
+uv run 04_generate_parquet.py --ud-ver "${NEW_VER}" --prune-extra --check-extra
 uv run 05_validate_parquet.py --ud-ver "${NEW_VER}" --local
 
 # Stage generated outputs
@@ -59,7 +59,7 @@ for UD_VER in 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17; do
   uv run 03_generate_README.py -o --ud-ver "${UD_VER}"
   cp README-${UD_VER} ../README.md
   cp metadata-${UD_VER}.json ../metadata.json
-  uv run 04_generate_parquet.py --ud-ver "${UD_VER}" --overwrite
+  uv run 04_generate_parquet.py --ud-ver "${UD_VER}" --overwrite --prune-extra --check-extra
   uv run 05_validate_parquet.py --ud-ver "${UD_VER}" --local
   cd ..
 
@@ -119,7 +119,8 @@ done
 - Converts CoNLL-U files to Parquet format
 - Creates: `../parquet/{treebank}/{split}.parquet`
 - Uses `tools/metadata-{UD_VER}.json` when present; otherwise falls back to `../metadata.json`
-- Options: `--ud-ver`, `--test`, `--overwrite`, `--blocked-treebanks`
+- Options: `--ud-ver`, `--test`, `--overwrite`, `--blocked-treebanks`, `--check-extra`, `--prune-extra`
+- Recommended for release runs: `--prune-extra --check-extra` to prevent stale parquet files when treebanks are renamed/removed across UD versions
 
 ### 05 - Validate Parquet
 
@@ -185,7 +186,7 @@ pip install ud-hf-parquet-tools pyyaml python-dotenv jinja2
 
 **Test on subset:**
 ```bash
-uv run ./04_generate_parquet.py --ud-ver 2.17 --test
+uv run ./04_generate_parquet.py --ud-ver 2.17 --test --prune-extra --check-extra
 uv run ./05_validate_parquet.py --ud-ver 2.17 --test --local
 ```
 
@@ -198,7 +199,7 @@ uv run ./05_validate_parquet.py --ud-ver 2.17 --local
 ```bash
 ./02_generate_metadata.py --ud-ver 2.17 -o
 ./03_generate_README.py --ud-ver 2.17 -o
-uv run ./04_generate_parquet.py --ud-ver 2.17 --overwrite
+uv run ./04_generate_parquet.py --ud-ver 2.17 --overwrite --prune-extra --check-extra
 ```
 
 **Skip blocked treebanks:**