Add a peer-cli-tests just recipe as the public entry point for the existing
extended scenario runner. The recipe depends on peer-cli-image, so Docker
uses its normal layer cache to decide whether the image needs rebuilding
before the Python harness runs.
This gives contributors one memorable command for the full S1-S47 matrix
while still allowing selected scenarios as positional arguments. The
underlying runner continues to own container topology and JSONL command/event
handling.
Test Plan:
- just --list
- just --dry-run peer-cli-tests S39 S40
- git diff --check
Refs: PEER_CLI_SCENARIOS.md
ddidderr
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