correctness pass: every printed command runs, no traceback ever reaches an agent

- the tool names itself in every command it prints. After `curl | sh`
  nothing is on PATH, so `Run: memo nap 0-1 ...` was command-not-found for
  every new user: the whole note -> merge -> nap loop died on the first turn.
- a typo in `config` stopped every command AND the recovery it named
  (`memo config`) read the same file, so nothing could fix it. It now names
  the file and the line.
- a filesystem error (read-only store, MEMORY_DIR at a file) printed a Python
  traceback. One handler reports it in the tool's own voice.
- `nap 1-2` answered 'already settled': an unaligned id read a different
  block's record. nap and forget now share one block-id parser.
- recall held the whole log in memory: 618 MB at a million memories, and a
  vague regex held every match too. One streaming pass, 16 MB.
- install.sh says so when the machine has no python3, instead of installing
  and then failing in env(1).
- anim: package.json was npm-init boilerplate; a comment named deleted blocks.py.