feat(agent-test): add the local-adapter CLI

Description

The pitch.

## Problem

Developers need a documented command to attach a strict local adapter, run the Town test, and consume stable human or machine-readable results.

## Change

- add `nest test agent --endpoint` with human and exact-byte JSON output
- ship a strict Python reference adapter and version 1 resources
- document setup, exit codes, trust boundaries, artifacts, and troubleshooting
- add real subprocess and clean installed-wheel journey checks

## Verification

- final stack: `make ci-local` — all 5 checks passed; 2,081 passed, 2 skipped, 1 deselected
- CLI, SIGINT, output-byte, reference-adapter, docs, and package-resource tests pass
- clean committed-archive/installed-wheel quickstart: PASS

## Stack

**5 of 9. Depends on PR 4.** PRs 6–9 add the existing-OpenClaw one-command journey. Custom adapters remain supported through this endpoint mode.

**Merge note:** After #223 merges into `main`, retarget this PR to `main`, wait for its CI, and only then merge it.