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/generate_member_files.py

@@ -1,23 +1,46 @@
+"""Generate markdown participant and leader profile files for the cohort.
+
+Reads all evaluation data files and produces two markdown files summarising
+each member's tech stack, availability, proficiency, and leadership assessment.
+
+Data files (place in data/):
+  - discord_verification.json   Discord ID verification results (from verify_discord.py)
+  - proficiency_evaluations.json  Proficiency scores (from evaluate_technical_proficiency.py)
+  - availability_analysis.json  Availability UTC blocks (from analyse_availability.py)
+  - leadership_candidates.json  List of applicants who expressed interest in leading
+  - leadership_evaluations.json  Leadership assessment scores
+
+Outputs (written to data/):
+  - participants.md  Markdown profile for each participant
+  - leaders.md       Markdown profile for each leader candidate
+
+Env vars:
+  - None
+"""
+
 import json
+from pathlib import Path
+
+DATA_DIR = Path(__file__).parent.parent.parent / "data"
 
 BLOCK_EMOJIS = {"mornings": "🌅", "afternoons": "☀️", "evenings": "🌆", "nights": "🌙"}
 
 
 def load_all_data():
     """Load all evaluation data files"""
-    with open("discord_verification.json") as f:
+    with open(DATA_DIR / "discord_verification.json") as f:
         verification = json.load(f)
 
-    with open("proficiency_evaluations.json") as f:
+    with open(DATA_DIR / "proficiency_evaluations.json") as f:
         proficiency = json.load(f)
 
-    with open("availability_analysis.json") as f:
+    with open(DATA_DIR / "availability_analysis.json") as f:
         availability = json.load(f)
 
-    with open("leadership_candidates.json") as f:
+    with open(DATA_DIR / "leadership_candidates.json") as f:
         candidates = json.load(f)
 
-    with open("leadership_evaluations.json") as f:
+    with open(DATA_DIR / "leadership_evaluations.json") as f:
         leadership = json.load(f)
 
     return verification, proficiency, availability, candidates, leadership
@@ -230,14 +253,14 @@ def main():
     participants_md = generate_participants_md(
         non_leader_ids, verified_usernames, prof_by_id, avail_by_id
     )
-    with open("participants.md", "w") as f:
+    with open(DATA_DIR / "participants.md", "w") as f:
         f.write(participants_md)
     print(f"Generated participants.md with {len(non_leader_ids)} participants")
 
     leaders_md = generate_leaders_md(
         leader_ids, verified_usernames, prof_by_id, avail_by_id, lead_by_id
     )
-    with open("leaders.md", "w") as f:
+    with open(DATA_DIR / "leaders.md", "w") as f:
         f.write(leaders_md)
     print(f"Generated leaders.md with {len(leader_ids)} leaders")