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/assign_cohort_role.py

@@ -6,9 +6,12 @@ Respects Discord rate limits with proper backoff and retry logic.
 import json
 import os
 import time
+from pathlib import Path
 
 import requests
 
+DATA_DIR = Path(__file__).parent.parent.parent / "data"
+
 BOT_TOKEN = os.environ["DISCORD_BOT_TOKEN"]
 GUILD_ID = "692816967895220344"
 COHORT_ROLE_ID = "1464314780935258112"
@@ -48,7 +51,7 @@ def assign_role_with_retry(user_id: str, role_id: str, max_retries: int = 5) ->
 
 
 def main():
-    with open("team_assignments.json") as f:
+    with open(DATA_DIR / "team_assignments.json") as f:
         teams = json.load(f)
 
     all_users = []