feat: port remaining cohort scripts and make reusable

- Port 19 cohort scripts from /home/naomi/docs/cohort/
- Replace all hardcoded tokens and dotenv usage with os.environ
- Add pandas==3.0.1 dependency
- Add E501 to ruff ignore list for Discord message string content
- Make remove_resigned_members.py reusable (empty RESIGNED_IDS constant)
- Make update_roster_messages.py reusable (iterates all teams from JSON)
- Exclude 12 one-off/event-specific scripts as non-reusable

python/cohort/remove_resigned_members.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+"""Remove resigned members from team_assignments.json.
+
+Update RESIGNED_IDS with the Discord IDs of members who have resigned
+before running this script.
+"""
+
+import json
+
+# Discord IDs of members who have resigned - update before running
+RESIGNED_IDS: list[str] = []
+
+
+def main() -> None:
+    """Remove resigned members from team assignments."""
+    with open("team_assignments.json") as f:
+        teams = json.load(f)
+
+    changes_made = []
+
+    for team in teams:
+        team_name = team["name"]
+
+        original_leaders = len(team["leaders"])
+        team["leaders"] = [lid for lid in team["leaders"] if lid not in RESIGNED_IDS]
+        if len(team["leaders"]) < original_leaders:
+            removed = original_leaders - len(team["leaders"])
+            changes_made.append(f"Removed {removed} leader(s) from {team_name}")
+
+        original_participants = len(team["participants"])
+        team["participants"] = [
+            pid for pid in team["participants"] if pid not in RESIGNED_IDS
+        ]
+        if len(team["participants"]) < original_participants:
+            removed = original_participants - len(team["participants"])
+            changes_made.append(f"Removed {removed} participant(s) from {team_name}")
+            print(f"⚠️  {team_name}: Proficiency distribution may need updating")
+
+    with open("team_assignments.json", "w") as f:
+        json.dump(teams, f, indent=2)
+
+    if changes_made:
+        print("✅ Successfully removed resigned members from team_assignments.json")
+        print("\nChanges made:")
+        for change in changes_made:
+            print(f"  - {change}")
+    else:
+        print("No changes needed - resigned members were not found in team assignments")
+
+    print("\nUpdated team sizes:")
+    for team in teams:
+        total_members = len(team["leaders"]) + len(team["participants"])
+        print(
+            f"  {team['name']}: {total_members} members "
+            f"({len(team['leaders'])} leaders, {len(team['participants'])} participants)"  # noqa: E501
+        )
+
+
+if __name__ == "__main__":
+    main()