feat: reorganise bash scripts and add comprehensive documentation (#6)

## Summary

This PR completes the bash script restructuring and adds comprehensive documentation across all script categories.

### Bash Restructuring

- Moved cohort shell scripts (`remove_github_members.sh`, `update_github_teams.sh`) from `python/cohort/` into a new `bash/cohort/` directory
- Moved existing bash utilities (`add-keys-to-git.sh`, `fix-yubikey-perms.sh`, `list-yubikey-ssh-keys.sh`) into a new `bash/yubikey/` subdirectory
- Updated `run.sh` to support **Bash** as a third language option alongside TypeScript and Python
  - Bash scripts are run directly (no 1Password secret injection needed)
  - Category discovery and script listing works the same as for TS/Python
  - Removed dead "Root Scripts" logic that was no longer needed

### Documentation

Added `README.md` files for all script categories that were missing them:

- `bash/cohort/README.md` — cohort GitHub team management scripts
- `bash/yubikey/README.md` — YubiKey SSH key and permission utilities
- `typescript/src/crowdin/README.md` — Crowdin translation management scripts
- `typescript/src/discord/README.md` — Discord bot utility scripts
- `typescript/src/discourse/README.md` — Discourse forum management scripts
- `typescript/src/gitea/README.md` — Gitea bulk repository operation scripts
- `typescript/src/github/README.md` — GitHub API interaction scripts
- `typescript/src/music/README.md` — Music file metadata tools
- `typescript/src/s3/README.md` — S3-compatible object storage scripts
- `typescript/src/security/README.md` — Security analysis and reporting scripts
- `python/cohort/README.md` — Updated to remove moved shell scripts, fix usage commands

Also updated project-level docs:

- **`README.md`** — Corrected project structure, fixed running instructions (removed references to non-existent `make run-ts`/`make run-py` targets), added Bash prerequisites
- **`CLAUDE.md`** — Updated project overview, structure, development standards, and script-adding guides to reflect the current state of the project

✨ This PR was created with help from Hikari~ 🌸

Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Reviewed-on: #6
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

python/cohort/check_lengths.py

@@ -0,0 +1,86 @@
+"""Dry-run check of Discord message lengths before sending the activity report.
+
+Parses the catch_up_report.md table, formats each team's data into a monospace
+Discord table, and reports whether any message would exceed Discord's 2000-char limit.
+Run this before send_activity_report.py to catch length issues early.
+
+Data files (place in data/):
+  - catch_up_report.md  Activity report generated by catch_up_report.py
+
+Env vars:
+  - None
+"""
+
+FIELDS = [
+    ("Discord Username", "Name", 18),
+    ("Discord Messages", "Msgs", 5),
+    ("PRs Opened", "PRs", 4),
+    ("Issues Opened", "Issues", 6),
+    ("Issue Comments", "Issue♟", 7),
+    ("PR Comments", "PR♟", 5),
+    ("PR Reviews", "Reviews", 7),
+    ("Commits", "Commits", 7),
+]
+
+REPORT_PATH = "data/catch_up_report.md"
+
+
+def parse_report(path: str) -> dict[str, list[dict]]:
+    """Parse the markdown table from catch_up_report.md into team → rows."""
+    teams: dict[str, list[dict]] = {}
+    with open(path, encoding="utf-8") as f:
+        lines = f.readlines()
+    header_line = None
+    for i, line in enumerate(lines):
+        if line.startswith("| Discord ID |"):
+            header_line = i
+            break
+    headers = [h.strip() for h in lines[header_line].strip().strip("|").split("|")]
+    for line in lines[header_line + 2 :]:
+        line = line.strip()
+        if not line.startswith("|"):
+            break
+        vals = [v.strip() for v in line.strip().strip("|").split("|")]
+        row = dict(zip(headers, vals))
+        teams.setdefault(row["Team"], []).append(row)
+    return teams
+
+
+def format_table(members: list[dict]) -> str:
+    """Format a team's member list as a monospace table for Discord."""
+    members = sorted(members, key=lambda r: int(r["Discord Messages"]), reverse=True)
+    col_widths = [w for _, _, w in FIELDS]
+    col_headers = [h for _, h, _ in FIELDS]
+    max_name = max(len(m["Discord Username"]) for m in members)
+    col_widths[0] = max(col_widths[0], max_name)
+
+    def pad(val: str, width: int, right_align: bool = False) -> str:
+        return val.rjust(width) if right_align else val.ljust(width)
+
+    header_row = "  ".join(
+        pad(col_headers[i], col_widths[i], right_align=(i > 0))
+        for i in range(len(FIELDS))
+    )
+    separator = "  ".join("-" * w for w in col_widths)
+    rows = []
+    for m in members:
+        vals = [m[key] for key, _, _ in FIELDS]
+        row = "  ".join(
+            pad(vals[i], col_widths[i], right_align=(i > 0)) for i in range(len(FIELDS))
+        )
+        rows.append(row)
+    return "\n".join([header_row, separator] + rows)
+
+
+def main() -> None:
+    """Check Discord message lengths for all teams."""
+    teams = parse_report(REPORT_PATH)
+    for team, members in teams.items():
+        table = format_table(members)
+        msg = f"**{team} — Activity Report (Feb 15–23)**\n```\n{table}\n```"
+        status = "OK" if len(msg) <= 2000 else f"OVER by {len(msg) - 2000}"
+        print(f"{team}: {len(msg)} chars — {status}")
+
+
+if __name__ == "__main__":
+    main()