Add custom script packages with Nix dependency management

This commit introduces two new custom script packages: tb-scripts for
all systems and tb-dev-scripts for development machines. These packages
provide a maintainable way to distribute utility scripts across the
infrastructure with proper dependency management.

## New Package Structure

Created pkgs/ directory with two script collections:

1. **tb-scripts** - General utilities available on all systems:
   - ,jq_reformat: Reformat JSON files in-place with atomic file operations
   - ,rename_lower: Convert filenames to lowercase with validation

2. **tb-dev-scripts** - Development-specific tools:
   - ,cmake_update_fetchcontent: Update CMake FetchContent dependencies

## Script Improvements

All scripts have been significantly enhanced from their original versions:

### ,jq_reformat (refactored from shell script)
- Proper quoting to handle filenames with spaces
- Secure temporary file creation using mktemp
- Atomic file replacement to prevent data loss
- Input validation and comprehensive error handling
- Usage help with -h/--help flag
- Extensive inline comments explaining each section
- Cleanup traps on error

### ,rename_lower (converted from Perl to Python)
- Complete rewrite in Python for consistency
- Validates files exist before attempting rename
- Checks if target lowercase filename already exists
- Skips files already lowercase (no-op)
- Descriptive error messages for each failure case
- Usage documentation with examples
- Proper exit codes

### ,cmake_update_fetchcontent (new)
- Interactive CMake FetchContent dependency updater
- Recursively finds all CMakeLists.txt files via add_subdirectory()
- Queries GitHub API for latest releases/tags
- Compares semantic versions and commit hashes
- Shows available updates in formatted table
- Prompts for confirmation before applying updates
- Atomic file updates with validation

## Nix Integration

Scripts are packaged using writeShellApplication with proper dependency
injection via runtimeInputs:

- tb-scripts requires: jq, python3
- tb-dev-scripts requires: python3, git

Dependencies are automatically available in PATH when scripts run,
eliminating manual dependency checks.

## Module Organization

Created system module files to import the script packages:

- system/default/scripts.nix: Adds tb-scripts to nixosModules.default
- system/develop/scripts.nix: Adds tb-dev-scripts to nixosModules.develop

Updated flake.nix to import these modules in the appropriate contexts.

## Benefits

- Scripts have proper Nix-managed dependencies
- No manual installation or PATH configuration needed
- Easy to extend with additional scripts
- Scripts are validated with shellcheck during build
- Clear separation between all-systems and dev-only utilities
- Comprehensive error handling and user documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

pkgs/tb-scripts/rename_lower.py

@@ -0,0 +1,115 @@
+#!/usr/bin/env python3
+
+"""
+rename_lower - Rename files to lowercase
+
+Usage: rename_lower FILE [FILE...]
+
+This script renames files by converting their filenames to lowercase.
+It performs validation to ensure files exist and that the target lowercase
+filename doesn't already exist before renaming.
+
+Examples:
+  rename_lower MyFile.TXT
+  rename_lower *.JPG
+  rename_lower Document.PDF Image.PNG
+"""
+
+import os
+import sys
+from pathlib import Path
+
+
+def usage():
+    """Show usage information"""
+    print("""Usage: ,rename_lower FILE [FILE...]
+
+Rename files to lowercase filenames.
+
+This script converts filenames to lowercase. It validates that files
+exist and checks for conflicts before renaming.
+
+Arguments:
+  FILE    One or more files to rename
+
+Options:
+  -h, --help    Show this help message
+
+Examples:
+  ,rename_lower MyFile.TXT
+  ,rename_lower *.JPG
+  ,rename_lower Document.PDF Image.PNG
+
+Exit codes:
+  0    Success - all files renamed (or already lowercase)
+  1    Error - invalid arguments, missing files, or conflicts
+""")
+
+
+def rename_to_lowercase(filepath: str) -> bool:
+    """
+    Rename a single file to lowercase.
+
+    Arguments:
+        filepath: Path to the file to rename
+
+    Returns:
+        True on success, False on error
+    """
+    # Convert to Path object for easier manipulation
+    original = Path(filepath)
+
+    # Validate that the file exists
+    if not original.exists():
+        print(f"Error: File not found: {filepath}", file=sys.stderr)
+        return False
+
+    # Get the directory and filename components
+    directory = original.parent
+    original_name = original.name
+    lowercase_name = original_name.lower()
+
+    # Check if the filename is already lowercase
+    if original_name == lowercase_name:
+        # Already lowercase, nothing to do
+        return True
+
+    # Construct the target path
+    target = directory / lowercase_name
+
+    # Check if target already exists
+    if target.exists():
+        print(f"Error: Target file already exists: {target}", file=sys.stderr)
+        print(f"  Cannot rename: {filepath}", file=sys.stderr)
+        return False
+
+    # Perform the rename
+    try:
+        original.rename(target)
+        print(f"Renamed: {original_name} -> {lowercase_name}")
+        return True
+    except OSError as e:
+        print(f"Error: Failed to rename {filepath}: {e}", file=sys.stderr)
+        return False
+
+
+def main():
+    """Main script logic"""
+    # Handle help flag or no arguments
+    if len(sys.argv) == 1 or sys.argv[1] in ("-h", "--help"):
+        usage()
+        return 0 if len(sys.argv) > 1 else 1
+
+    success = True
+
+    # Process each file argument
+    for filepath in sys.argv[1:]:
+        if not rename_to_lowercase(filepath):
+            success = False
+            # Continue processing other files even if one fails
+
+    return 0 if success else 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())