docs: add data file documentation and fix data path resolution

All Python cohort scripts now use DATA_DIR = Path(__file__).parent.parent.parent / "data"
to correctly resolve the repo-root data/ directory regardless of the working directory
set by run.sh. All TypeScript scripts have expanded JSDoc headers documenting data file
requirements and environment variables.

python/cohort/get_cohort_members.py

@@ -4,9 +4,12 @@
 import asyncio
 import json
 import os
+from pathlib import Path
 
 import aiohttp
 
+DATA_DIR = Path(__file__).parent.parent.parent / "data"
+
 DISCORD_BOT_TOKEN = os.environ["DISCORD_BOT_TOKEN"]
 GUILD_ID = "692816967895220344"
 COHORT_ROLE_ID = "1464314780935258112"
@@ -72,7 +75,7 @@ async def main() -> None:
                 f"{i}. {member['display_name']} (@{member['username']}) - ID: {member['id']}"  # noqa: E501
             )
 
-        with open("active_cohort_members.json", "w") as f:
+        with open(DATA_DIR / "active_cohort_members.json", "w") as f:
             json.dump(cohort_members, f, indent=2)
 
         print("\nSaved to active_cohort_members.json")