Add inspect subcommand: read-only stats for v2 map files

Reads the map JSON, optionally loads --atlas-dir paths for name
resolution, and prints the inspector report to stdout. Missing
file, bad JSON, and missing --atlas-dir paths all produce
labelled stderr errors with exit 1.

tests/inspect.test.js

@@ -0,0 +1,53 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const path = require('node:path');
+const { run } = require('../src/cli');
+
+class Sink {
+  constructor() { this.chunks = []; }
+  write(s) { this.chunks.push(s); }
+  get text() { return this.chunks.join(''); }
+}
+
+const FIX_MAP = path.join(__dirname, 'fixtures', 'maps', 'inspect_sample.map.json');
+const FIX_ATLAS = path.join(__dirname, 'fixtures', 'atlases');
+
+test('inspect: prints report to stdout, exit 0', () => {
+  const out = new Sink(); const err = new Sink();
+  const code = run(['inspect', FIX_MAP], { out, err });
+  assert.equal(code, 0, err.text);
+  assert.match(out.text, /Map: inspect_sample/);
+  assert.match(out.text, /Roof: 4 cells flagged/);
+});
+
+test('inspect: --atlas-dir enables name resolution', () => {
+  const out = new Sink(); const err = new Sink();
+  const code = run(['inspect', FIX_MAP, '--atlas-dir', FIX_ATLAS], { out, err });
+  assert.equal(code, 0);
+  assert.match(out.text, /atlas_a:grass/);
+});
+
+test('inspect: missing positional arg prints usage, exit 1', () => {
+  const out = new Sink(); const err = new Sink();
+  const code = run(['inspect'], { out, err });
+  assert.equal(code, 1);
+  assert.match(err.text, /usage: sporel-mapper inspect/);
+});
+
+test('inspect: missing map file prints error, exit 1', () => {
+  const out = new Sink(); const err = new Sink();
+  const code = run(['inspect', '/no/such/map.json'], { out, err });
+  assert.equal(code, 1);
+  assert.match(err.text, /error: cannot read/);
+});
+
+test('inspect: invalid JSON prints error, exit 1', () => {
+  const out = new Sink(); const err = new Sink();
+  // Use a non-JSON file as bogus input
+  const reallyNotJson = path.join(__dirname, '..', 'src', 'cli.js');
+  const code = run(['inspect', reallyNotJson], { out, err });
+  assert.equal(code, 1);
+  assert.match(err.text, /error/i);
+});