Script understanding memory

Teach Arka about scripts it uses repeatedly.

Teach Arka about scripts it uses repeatedly:

arka understand-script show scripts/build.py
arka understand-script remember scripts/build.py
arka understand-script list

Arka records a local summary of functions, imports, line count, and CLI hints. Future coding and routing tasks can use this summary instead of rediscovering the same script structure. It does not execute the script while analyzing it. Natural language such as “remember this script tools/build.py” is supported.