gndc - Stage 4 - Draft natural-language specs per subroutine

Loop over `subs` (except `main`) and run:

**Prompt 4A – NL spec for one subroutine**

```
You are a Gendo spec writer. Write a concise,
step-by-step natural-language algorithm for
subroutine **{name}** that fulfils its purpose.
Mention exactly the opcodes it will use
({ops_for_sub}). Do not write code yet.
```

**Expected output** Bulleted pseudocode outlining each line.

