```python
# /// intent
# goal   = "Write report.txt with one line per .cpp file under src, sorted by name, in the form '<name>: <number of characters>'"
# reads  = ["src/*.cpp"]
# writes = ["report.txt"]
# output = "printed"
# ///

from pathlib import Path

# Get all .cpp files under src, sorted by name
paths = Path("src").glob("*.cpp")
sorted_paths = sorted(paths)

# Write one line per file: '<name>: <number of characters>'
with Path("report.txt").open("w") as f:
    for p in sorted_paths:
        text = p.read_text()
        f.write(f"{p.name}: {len(text)}\n")
```