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/send_activity_report.py

@@ -1,4 +1,14 @@
-"""Send formatted activity report tables to each team channel via Amari bot."""
+"""Send formatted activity report tables to each team's Discord channel.
+
+Parses catch_up_report.md and posts a monospace table of each member's Discord
+and GitHub activity stats to their respective team channel.
+
+Data files (place in data/):
+  - catch_up_report.md  Activity report generated by catch_up_report.py
+
+Env vars:
+  - DISCORD_BOT_TOKEN  Bot token for the Discord API
+"""
 
 import asyncio
 import os
@@ -25,7 +35,9 @@ CHANNEL_IDS = {
     "Sage Marigold": "1464316850669093040",
 }
 
-REPORT_PATH = os.path.join(os.path.dirname(__file__), "catch_up_report.md")
+REPORT_PATH = os.path.join(
+    os.path.dirname(__file__), "..", "..", "data", "catch_up_report.md"
+)
 
 FIELDS = [
     ("Discord Username", "Name", 18),